msm: kgsl: Avoid cx gdsc off timeout if SMMU driver has a vote

Smmu driver keeps a vote on cx gdsc to block cx gdsc collapse
when CONFIG_ARM_SMMU_POWER_ALWAYS_ON is enabled. So don't bother
polling for cx gdsc collapse during the slumber sequence when this
config is enabled.

Change-Id: Iacbbfcc76600e0e567610265d5da87146946df66
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>