ANDROID: GKI: mm/memblock: export memblock_overlaps_memory

The PIL driver needs it, export the symbol to enable compilation as a
module.

Bug: 144523239
Change-Id: I43692fa55d17c3196719c6606766d4fd5c5f6c65
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>