msm: kgsl: Change an overflow check to be "smart" compiler proof

In its infinite wisdom, GCC will optimize out this overflow check:

   if ((gpuaddr + size) < gpuaddr)

Which might totally make sense for the compiler but it doesn't do us
a bit of good. Replace the existing overflow check with something
that GCC can't ignore.

CRs-fixed: 544025
Signed-off-by: Gaurav Gagrani <ggagrani@codeaurora.org>
Change-Id: Ifd8a8a1ff2a99b2fc56473124317dd9376c03443
Signed-off-by: Gaurav Gagrani <ggagrani@codeaurora.org>
Merge "msm: kgsl: Change an overflow check to be "smart" compiler proof"