msm: kgsl: Make the snapshot better at detecting packet boundaries

Enhance the logic that checks to see if the CP_RPTR is stuck
mid packet.  Ensure that when we do packet counting that we
use real type3 packets instead of regular data pretending to
be a type3 packet.

Change-Id: Ic0dedbadb502fa2790df0c6752309da300d6d1ae
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>