mxs: Add NAND fdt and ramdisk partition to m28evk

Adjust the NAND partitioning layout so that there is a separate partition
for the ramdisk and fdt blob on the NAND.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Detlev Zundel <dzu@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Wolfgang Denk <wd@denx.de>