msm: kgsl: Trigger preemption from command complete interrupt

Trigger preemption from the command complete interrupt on A6XX
in order to do fast preemption.

Change-Id: I7dffa97758820a0aaacf7a0e1160d0c85e610ca8
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>