mtd: plat_nand: use default partition probe

It's harmless to add 'ofpart' (the only different parser supported in
default mtdpart.c) to plat_nand. That let's us kill off one more custom
partition prober listing.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --cc drivers/mtd/nand/plat_nand.c
Simple merge

diff --cc drivers/mtd/nand/xway_nand.c
Simple merge