memblock: Add memblock_overlaps_memory()

Add a new function, memblock_overlaps_memory(), to check if a
region overlaps with a memory bank. This will be used by
peripheral loader code to detect when kernel memory would be
overwritten.

Change-Id: I851f8f416a0f36e85c0e19536b5209f7d4bd431c
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>