msm: kgsl: Clean up preemption

Move the preemption timer into the generic adreno code so we don't need
to destroy it in target specific code and generally get rid of a bunch
of static assumptions in the target specific code.

Change-Id: Ic0dedbad4fff2c85dcb9d5c1300c45ee659675bd
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>