msm: kgsl: Clear halt before gmu boot

During hard reset if we are not able to toggle the CX
gdsc, the halt will remain asserted at the time of next
GMU boot. This causes GMU boot to fail and lead to NoC
errors. So clear the halt bit before attempting GMU boot.

Change-Id: Id214e0a9261c1f14de13864c715cf1a9d415e1e7
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>
Signed-off-by: Pankaj Gupta <gpankaj@codeaurora.org>