DLPLCRDC4422EVM: Polarization and plug definition of 12V power supply

Per the EVM User's Guide section 4.1 (External Power Supply Requirements), the center pin is positive (+).  It should mate with a 5.5mm (OD) x 2.1mm (ID) x 9.5mm (length) barrel plug. 12V -5%/+10% 7A Max is recommended.  A power supply is recommended in the User's Guide.