msm: kgsl: Avoid unnecessary "AHB fence stuck in ISR" error logs

Kgsl driver polls GMU for fence status to become zero in case
it was one in IRQ handler and prints "AHB fence stuck in ISR"
error log in case it doesn't happen in multiple retries. Add a
small delay between two retries to make sure GMU firmware gets
sufficient time to abort power collapse. This will avoid this
error prints in scenarios where waiting loop finish much faster
and GMU is still in process of aborting power collapse. This
will also reduce number of retries.

Also, dump register GMU_AO_RBBM_INT_UNMASKED_STATUS_SHADOW as
part of error message to identify the unhandled IRQ when this
error happens.

Change-Id: Ia67a44db43d5a4ec3dd7f3323e7754d950490aec
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>