msm: kgsl: Cast perfcounter query count to an unsigned int

In adreno_perfcounter_query_group() make sure to cast the user passed
count to an unsigned int before comparing it to the group count.
Otherwise the user count could be interpeted as a signed int and
hilarity ensues.

Change-Id: Ic0dedbad825f5b3fd4434f9b9f6d4d308206c0d9
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>