powerpc/t104xrdb: Add Support of rcw for T1042RDB in u-boot

powerpc/t104xrdb: Add Support of rcw for T1042RDB in u-boot

This patch adds support of rcw for T1042RDB, it makes following changes :
- Adds t1042_rcw.cfg file for serdes protocol 0x86 for T1042RDB
- Renames t1042_pi_rcw.cfg file from t1042_rcw.cfg and also updates
  comments for valid serdes protocol which is 0x06
- Also updates CONFIG_SYS_FSL_PBL_RCW for T1042RDB

Signed-off-by: Vijay Rai <vijay.rai@freescale.com>
Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>