memblock: Implement memblock_is_memory and memblock_is_region_memory

memblock: Implement memblock_is_memory and memblock_is_region_memory

To make it fast, we steal ARM's binary search for memblock_is_memory()
and we use that to also the replace existing implementation of
memblock_is_reserved().

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>