msm: kgsl: Sanitize command batch flags passed in by users

KGSL uses a specific set of command batch flags to do smart things.
These flags are passed into KGSL by users who could set command batch
flags that KGSL does not understand. So only accept flags that KGSL
knows how handle.

Change-Id: Ic9b7e56dfdf3926b142e2a5bf593559a63ef7f37
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>