msm: kgsl: Keep dispatcher halted during SUSPEND state

Increment GPU halt variable after successful transition
to SUSPEND state to halt dispatcher. This is necessary to
make sure that any pending dispatcher threads don't go
ahead and try to wake up GPU in SUSPEND state.

Change-Id: I806884306549afbef0dfa92ea14903cc7a47d347
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>