ARM: OMAP: FB sync with N800 tree (support for dynamic SRAM allocations)

- in addition to fixed FB regions - as passed by the bootloader -
  allow dynamic allocations
- do some more checking against overlapping / reserved regions
- move the FB specific parts out from sram.c to fb.c

Signed-off-by: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>