Requirement of gpmc header outside of mach-omap2 has been
cutoff, move gpmc header file in plat-omap folder to local
mach-omap2 folder

Objective - common zImage participation of omap
Signed-off-by: NAfzal Mohammed <afzal@ti.com>

For common arm zImage existing nand header file
in platform specific location was moved to generic
platform data location, but it contained more than
platform data, remove it. New local header has been
created for exposing functions.

Also move gpmc-nand platform data to platform header
meant for nand from gpmc header file
Signed-off-by: NAfzal Mohammed <afzal@ti.com>