msm: kgsl: Fix sizes of flag constants

Flag constants were used without being typecast to the correct types
at a few places. Add appropriate typecasts to make sure we set or clear
the bits we expect.

Change-Id: Ibfde9c561df0da6c59a9154bdd777c290bf15ad7
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>