fix sparse, checkpatch warnings in OMAP2/3 SMS/GPMC/SRAM code

Fix sparse warnings in SMS, GPMC, SRAM code involving arch/arm/mach-omap2/.
These fixes mostly consist of:

- tagging appropriate integer<->pointer casts with __force

- marking private structures and functions as static; adding function
  prototypes in .h files for public functions

- assigning NULL to pointers in structure initializers, not 0

- adding prototypes for *_init() functions in the appropriate header
  files, and getting rid of the corresponding open-coded extern
  prototypes in other C files

Also clean up some checkpatch issues by converting some asm/ includes
to linux/ includes.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>