Marvell RD6281A Board support

This is Marvell's 88F6281_A0 based reference design board

This patch is tested for-
1. Boot from DRAM/NAND flash/NFS
2. File transfer using tftp and loadb
3. NAND flash read/write/erase

Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>