msm: kgsl: keep usermode context flags in kgsl_context

Store flags from userspace context creation in kgsl_context.flags,
and move all internal flags to adreno_context.priv.

Change-Id: I3c73ebee4092abf5864238319c214c4d977bdaad
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>