ARM: OMAP2+: gpmc-nand: update gpmc-nand regs

GPMC has NAND registers, update nand platform data with those details
so that NAND driver can configure those by itself instead of using
exported symbols.

Signed-off-by: Afzal Mohammed <afzal@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>