ANDROID: mm/memblock: export memblock_end_of_DRAM

Export memblock_end_of_DRAM() so that module drivers can know
the physical end address of memory blocks that system booted with.

Bug: 174547201
Change-Id: Ib0c90b736f16d1abbf47d4f3288443c35f9e17b4
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>