msm: kgsl: Wait longer for CX headswitch off

Due to scheduler latency, GPU driver has to wait longer
for SMMU driver to release CX headswitch vote. The
change also calls cond_resched() API to yield to scheduler
to provide SMMU driver better chance to finish its job.

CRs-Fixed: 2064195
Change-Id: Iee630f14a9958db42cb317686c90aed284471bf5
Signed-off-by: George Shen <sqiao@codeaurora.org>