lib: genalloc: Change chunk allocation to vmalloc

Change the chunk allocation from kmalloc to vmalloc for
allocations greater than a page. This allows large
chunks to be allocated from physically non-contiguous
memory and increases the chance of the allocation
succeeding.

(cherry picked from commit 0614b96dc8e4c8a0dd0db41aec5a79daa3bdf091)

Conflicts:

	lib/genalloc.c

(cherry picked from commit 64cf7183f37df623bec8f46348b11c5781d3b0cc)

Change-Id: Ied97c888b967c4433519cb47e972f7a0f2281d71
CRs-fixed: 387655
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>