msm: kgsl: Check if GPU is hung when reserving space in rb

A busy loop is executed when we allocate space from the ringbuffer.
If the GPU is hung then we can wait indefinitely in the busy loop.
Add a wait time to this busy loop, and if the wait time elapses then
report a GPU hang instead of waiting indefinitely.

Change-Id: I035c39063cbfa25380702720f929df5319e73e61
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>