msm: kgsl: Fix black screen when enabled protected context on A680

This bit should only be set when CM3_CGC clock gating is enabled,
Otherwise always live CM3 clock will make dead loop in CM3 clock
control FSM, No Effect If this bit is set to 0, this is the default
behavior.

Change-Id: I9052182bd05e38433e11bbfdfa1f1c48c980fc9b
Signed-off-by: Hui Li <hul@codeaurora.org>