msm: kgsl: Move the adreno WPTR poke logic to the hang detection

Sometimes a write to CP_WPTR fails to latch on A20x GPUs. In the past
we worked around this by writing to WPTR numerous times in the various
loops that waited for GPU activity.  Consolidate these disparate calls
by moving the poke into the hang detect function.  If the core is idle
but the RPTR != WPTR, then rewrite the WPTR and go back through the
loop again.

Change-Id: Ic0dedbad474c7884c2467fe050d8afe673588add
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>