msm: kgsl: Do not halt entire GPU on unprotected write

Do not halt entire GPU on unprotected write when in trusted
mode. If you halt the GPU when such access happens, GPU
blocks all further traffic until complete HW reset.

CRs-fixed: 730322
Change-Id: I9b77cdfa36fa7cfab4e9768bcc3595cdeb25dae7
Signed-off-by: Rajeev Kulkarni <krajeev@codeaurora.org>