msm: kgsl: Streamline OOB set/clear calls

Abstract out all the magic of an OOB set/clear to simplify the
interface. This will remove the chance of programming error. This
also reduces the complexity to add/remove additional OOB bits.

Change-Id: I15adf614b1def93ca56d87a02c9599077eb64dc7
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>