msm: kgsl: Check again if HFI fails to find ack

When an interrupt comes to tell the host that there
is a new HFI message from the GMU, KGSL schedules
a tasklet to process the message queues.
If the message is an ack, the sender of the message
being acked is waiting for a completion to be signaled.
But when the system is very busy, the HFI tasklet might not get
to run before the completion times out.

When sending a message, check the queues one more
time before returning failure to prevent these false
instances of not receiving an ack. In order to make sure
this second check does not read the queues at the same
time as the tasklet, add a new HFI spinlock.

Change-Id: Ib0537af9137e5e243067519c26dc4939217b76e7
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>