OMAP: VRAM: Fix boot-time memory allocation

Use memblock_free() and memblock_remove() to remove the allocated or
reserved VRAM area from normal kernel memory.

This is a slightly modified version of patches from Felipe Contreras and
Namhyung Kim.

Reported-by: Felipe Contreras <felipe.contreras@gmail.com>
Reported-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>