msm: kgsl: Move hardware idle detection in to hardware specific driver.

Add callback to report HW idle status. When GMU is enabled RBBM_SATUS
register may not be accessible cause GX part of GPU can be power collapsed.
Use always on status register powered by MX rail.

CRs-Fixed: 2017390
Signed-off-by: Oleg Perelet <operelet@codeaurora.org>
Change-Id: Ic5443cb0053e47362b557d1315823c120b459097