msm: kgsl: Report GPU frequency correctly in sysfs

On our device, slumber is enabled (qcom,strtstp-sleepwake).

Change-Id: Id4444c602ff4dfcd9b74ab8d8124a0061e287bda

Signed-off-by: flar2 <asegaert@gmail.com>

Conflicts:
	drivers/gpu/msm/kgsl_pwrctrl.c