As per the data sheet of TDA4VM -->

/*
	MCSPI3 and MCSPI4 include internal connectivity to MCSPI modules in the MCU domain, as follows:
	MCSPI3 is connected as a master to MCU_MCSPI1 by default at power-up. MCU_MCSPI1 and MCSPI3
	may be optionally mapped to external device pads.
	
	MCSPI4 is directly connected as a slave to MCU_MCSPI2 by default at power-up. MCSPI4 and
	MCU_MCSPI2 are not pinned out externally.
*/

Instance 3 is for mpu1_0 as master and instance 1 is for mcu1_0 as slave -->

The changes I made in file "main_mcspi_slave_mode.c" are --> 

/**********************************************************************

static uint32_t SPI_test_get_instance (uint32_t testId, bool master)
{
      uint32_t instance;

      /* Soc configuration structures indexing starts from 0. If the IP
       * instances start with 1, to address proper Configuration
       * structure index, McSPI Instance should be substracted with 1
       */
       if (master == (bool)true)
       {
           instance = (uint32_t)BOARD_MCSPI_MASTER_INSTANCE - 1;
       }
      else
       {
          instance = (uint32_t)BOARD_MCSPI_SLAVE_INSTANCE - 1;
       }
#if defined (SOC_AM65XX) || defined(SOC_J721E) || defined(SOC_J7200)
/*
* For AM65XX/J721E/J7200 SoC, master/slave test is set up to use
* McSPI 2 on the MCU domain for master and McSPI 4 on the
* Main domain for slave, for loopback test it uses default
* board McSPI instance
*/
      if (testId < SPI_TEST_ID_LOOPBACK)
      {
         if (master == true)
         {

               instance = 3U;     //changes done to make mpu1_0 as mater
//             instance = 2U;
         }
        else
        {

              instance = 1U;    //changes done to make mcu1_0 as slave
//            instance = 4U;
        }
        if ((testId == SPI_TEST_ID_TIMEOUT) ||
           (testId == SPI_TEST_ID_TIMEOUT_POLL))
        {
/*
* Timeout test is done in slave mode,
* on the McSPI 2 on MCU domain
*/
            instance = 1U;
       }

    }
#endif

return (instance);
}

/**********************************************************************************************************

The changes made in makefile at location
"ti-processor-sdk-rtos-j721e-evm-07_03_00_07/pdk_jacinto_07_03_00_29/packages/ti/drv/spi/example/mcspi_slavemode"

/*********************************************************************************************************************
ifeq ($(CORE), mpu1_0)
# Slave running on mpu1_0 core


#CFLAGS_SPI_MS = -DMCSPI_SLAVE_TASK                    <----------------------- COMMENTED THIS
#APP_MASTER_SLAVE = Slave                                          <----------------------- COMMENTED THIS
CFLAGS_SPI_MS = -DMCSPI_MASTER_TASK                <----------------------- LINES CHANGED
APP_MASTER_SLAVE = Master                                        <----------------------- LINES CHANGED

ifeq ($(SOC),$(filter $(SOC), am65xx))
# Slave uses local linker command file to avoid code/data memory conflict with master application
EXTERNAL_LNKCMD_FILE_LOCAL = $(PDK_INSTALL_PATH)/ti/drv/spi/example/mcspi_slavemode/am65xx/linker_mpu.lds
endif
else
# Master running on mcu1_0 core, use the common linker command file in build



#CFLAGS_SPI_MS = -DMCSPI_MASTER_TASK                    <----------------------- COMMENTED THIS
#APP_MASTER_SLAVE = Master                                            <----------------------- COMMENTED THIS
CFLAGS_SPI_MS = -DMCSPI_SLAVE_TASK                         <----------------------- LINES CHANGED
APP_MASTER_SLAVE = Slave                                                <----------------------- LINES CHANGED


ifeq ($(SOC),$(filter $(SOC), j721e j7200))
# Slave uses local linker command file to avoid code/data memory conflict with master application
ifeq ($(IS_BAREMETAL),yes)
EXTERNAL_LNKCMD_FILE_LOCAL = $(PDK_INSTALL_PATH)/ti/drv/spi/example/mcspi_slavemode/$(SOC)/linker_mcu.lds
else
EXTERNAL_LNKCMD_FILE_LOCAL = $(PDK_INSTALL_PATH)/ti/drv/spi/example/mcspi_slavemode/$(SOC)/linker_mcu_sysbios.lds

endif
endif

************************************************************************************************************************/