msm: kgsl: Update condition to use CPU path for context switching

A5XX context switching involves flush/invalidate of ICACHE, CCU and LRZ
caches and this cannot be performed using AHB writes. Use CPU path only
when going to power collapse and to update context for non active
ringbuffer in preemption.

Change-Id: I2c34ec5d4f588d51b99f6bfd04ba9a75eaaea6cb
Signed-off-by: Tarun Karra <tkarra@codeaurora.org>