drm/ttm: make device_released static

fixes sparse warning, and removes potentially dangerous name from namespace.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ttm/ttm_module.c

@@ -35,7 +35,7 @@
 #include <drm/drm_sysfs.h>
 
 static DECLARE_WAIT_QUEUE_HEAD(exit_q);
-atomic_t device_released;
+static atomic_t device_released;
 
 static struct device_type ttm_drm_class_type = {
 	.name = "ttm",