powerpc/t104xrdb: Unification of T104xRDB header files

T1040RDB, T1042RDB header files are very similar so merged into new header file T104xRDB.
T104xRDB header file can support both T1040RDB and T1042RDB_PI header.

Patch makes following changes
-Update Boards.cfg file for T1040RDB and T1042RDB_PI
-Add new T104xRDB header file
-Delete T1040RDB, T1042RDB_PI header file

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>