msm: kgsl: Return error if the user allocates a buffer size of zero

Instead of calling BUG_ON if the user passes a zero length via
IOCTL_KGSL_GPUMEM_ALLOC to kgsl_sharedmem_alloc_user, return
-EINVAL instead and propegate the error back up to the user.

CRs-fixed: 389886
Change-Id: Ic0dedbad2dc1f68ad1d3227498893c73c2a1c59e
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rajeev Kulkarni <krajeev@codeaurora.org>
msm: kgsl: Limit GPU memory buffer allocation sizes

Limit the size of individual GPU memory allocations to the amount of
free memory on the system minus 32MB.  This early check gives us the
chance to verify that the user didn't ask for an obscene amount of
memory, and also to limit the chance that an allocation attempt will
invoke the OOM killer.

The 32MB buffer in particular should keep us out of the clutches of
the OOM killer. That number is the same amount of buffer used in
the page allocation alogrithms and it should keep the GPU from further
throwing fuel on the fire of a low memory situation.

Change-Id: Ic0dedbadcc5ee9cc0d77056b1a22eed5c385d636
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rajeev Kulkarni <krajeev@codeaurora.org>
msm: kgsl: Enable "big page" memory allocations

Allow users to specify "big page" mode when allocating GPU
memory. This will attempt to allocate contigious units of 64k
bytes per instead of the usual PAGE_SIZE units.  If the allocation
fails, then automatically fall back to allocate the rest of the
region with 4K pages. This means that potentially any allocation
could be comprised of a mixture of 64k chunks and 4k chunks.

Change-Id: Ib92c0c099d3b10ba54dbb864c5f977f8df4912f2
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>
Signed-off-by: Rajeev Kulkarni <krajeev@codeaurora.org>

Conflicts:
	drivers/gpu/msm/kgsl_sharedmem.c