msm: kgsl: use shmem for kgsl allocations

Use shmem for graphics allocations. This would help to make
kgsl pages moveable and also swappable to zram. By using
shmem we would forgo the benefit of using higher order pages
and pools. But the benefits we get from it in terms of getting
more free memory available in the system and getting larger
contiguous chunks of memory can outweigh what we forgo.

Change-Id: If613d721c581317967ea0603ea151fe85aca8afe
Signed-off-by: Puranam V G Tejaswi <pvgtejas@codeaurora.org>