board/bsc9131rdb: Add targets for Sysclk 100MHz

BSC9131RDB supports Sysclk
-66MHz if jumper J16 is close (default state)
-100MHz if jumper J16 is open

Add targets
-BSC9131RDB_NAND_SYSCLK100 : for NAND boot at Sysclk 100MHz
-BSC9131RDB_SPIFLASH_SYSCLK100: for SPI boot at Sysclk 100MHz

Signed-off-by: Ramneek Mehresh <ramneek.mehresh@freescale.com>
Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>