msm: kgsl: Return -EPROTO in certain functions if the GPU has faulted

Return -EPROTO as the error code for waittimestamp and issueibcmd
ioctl calls if the calling context had faulted since the last time
the bit was checked. The userspace driver can use this return code
to perform post-fault actions.

Change-Id: Ic0dedbadcd3b9137c7c37ec12fc92eb97dff6158
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>