msm: kgsl: Extend the preemption keep-alive bit

This is needed in order to avoid the spurious interrupts
seen during preemption.

Change-Id: Id8a465d1d3ea5b6994ab36d24d0efa1a84c9c6b6
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>