msm: kgsl: An error condition could cause an array overflow

In kgsl_setup_pt() if the MMU specific setup_pt function fails
the code will attempt to unwind the setup but it will use an
out of bounds index to do so.

Change-Id: Ic0dedbad8b23f65d4b52cb5ba01810ff26b19b89
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>