msm: kgsl: Add IB submission gate for device suspend

Add IB submission gate to stop the system from making requests
while suspend is requested.  This will force users to wait for
the system to resume before making more requests.

Change-Id: I2460ef9b4237b586a31d4cea64b6dd74d30b08d9
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>