msm: kgsl: use del_timer_sync() to cancel the idle timer

Otherwise there's a chance the idle timer can fire after
we're suspended/stopped on SMP systems.

Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>
diff --git a/drivers/gpu/msm/kgsl.c b/drivers/gpu/msm/kgsl.c
index 856972c..e4add0d 100644
--- a/drivers/gpu/msm/kgsl.c
+++ b/drivers/gpu/msm/kgsl.c
@@ -315,7 +315,7 @@
 		mutex_lock(&device->mutex);
 	}
 	/* Don't let the timer wake us during suspended sleep. */
-	del_timer(&device->idle_timer);
+	del_timer_sync(&device->idle_timer);
 	switch (device->state) {
 		case KGSL_STATE_INIT:
 			break;