msm: kgsl: Fix page align allocation overflow

KGSL does alignments for all user memory requests. If the
request is large enough the alignment operation will overflow
resulting in a valid request of size 0. It's just a matter of
time until the kernel or user tries to then do something useful
with this buffer resulting in a hang. Perform a sanity check
after doing the alignments to ensure the overflow did not occur.

Change-Id: I68f0f2c7dfdfb117e6d1320ec594cbdf75407a3e
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>