msm: kgsl: Check correct register for clamps on a660

A660 has a new register to check whether clamps were asserted
when toggling the gx rail.

Change-Id: Ie63853b79e386fdff0e0a5ab4c4fac62ba3a2b3f
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>