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.

CRs-fixed: 387655
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>
(cherry picked from commit 0614b96dc8e4c8a0dd0db41aec5a79daa3bdf091)

Conflicts:

	lib/genalloc.c

Change-Id: Ic0dedbad9d277d0842591b1f075ce3b80c8c05de
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>