Creating a patch for a C source file using openembedded, bitbake

I am trying to make a change in the x load for the for the sdram as follows:

change the configuration from 2 banks 128 MB each to 1 bank 256 MB.

I made the change as described below:

  In the function     void config_3430sdram_ddr(void)

   from

          __raw_writel(0x1, SDRC_CS_CFG); /* 128MB/bank */

          __raw_write(SDP_SDRC_MDCFG_0_DDR, SDRC_MCFG_0);

      __raw_write(SDP_SDRC_MDCFG_0_DDR, SDRC_MCFG_1);
 
   to
      __raw_writel(0x2, SDRC_CS_CFG); /* 256MB/bank */

    __raw_write(SDP_SDRC_MDCFG_0_DDR_NICRON_XM, SDRC_MCFG_0);
     __raw_write(SDP_SDRC_MDCFG_0_DDR_NICRON_XM, SDRC_MCFG_1);

then I created a patch

When I created a SDcard with the new MLO and tried it on my board it looked like the change did not take place, however the MLO file had a 
different checksum.

Can somebody tell me what I did wrong ???

thak you.