msm: kgsl: Don't halt dispatcher if device is not in SUSPEND state

Add a check to make sure device actually transitioned to SUSPEND
state before halting dispatcher in adreno_suspend_device function.
kgsl_pwrctrl_change_state(device,KGSL_STATE_SUSPEND) in
kgsl_suspend_device can return zero without actually changing state
to SUSPEND if device state is NONE or INIT.

Change-Id: I4a5a69007c71651ea2cf7fa7360c960c6856031e
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>
Signed-off-by: Archana Sriram <apsrir@codeaurora.org>