msm: kgsl: Fix racing in HFI message deletion

Move more HFI message processing into spinlock protected
area in tasklet function that receives HFI message
and notifies GMU driver thread. The racing happens
when GPU driver times out waiting for HFI message. Receiver
function just received the message and processing it.

CRs-Fixed: 2052606
Change-Id: I495ba923961f8c91f9806eee0766a96f2b4371d6
Signed-off-by: George Shen <sqiao@codeaurora.org>