msm: kgsl: Verify the user address before reading a perfcounter group

In adreno_perfcounter_read_group some user input verification is
occuring on a user pointer before copy_from_user is called
resulting in a possible segmentation fault if called with improper
input data.

CRs-fixed: 553314
Change-Id: Ic0dedbad4c5e4b2610368d51ff591d1f716712f4
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>