x86, memblock: Add memblock_x86_register_active_regions() and memblock_x86_hole_size()

memblock_x86_register_active_regions() will be used to fill early_node_map,
the result will be memblock.memory.region AND numa data

memblock_x86_hole_size will be used to find hole size on memblock.memory.region
with specified range.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>