drm: Reduce scope of 'state' variable

Smaller scope reduces visibility of variable and makes usage of
uninitialized variable less possible.

Changes in v2:
	- separate declaration and initialization
Changes in v3:
	- add missing signed-off-by tag
Signed-off-by: Dawid Kurek <dawikur@gmail.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170615174556.GA8872@gmail.com

drivers/gpu/drm/drm_atomic.c

@@ -109,9 +109,10 @@ struct drm_atomic_state *
 drm_atomic_state_alloc(struct drm_device *dev)
 {
 	struct drm_mode_config *config = &dev->mode_config;
-	struct drm_atomic_state *state;
 
 	if (!config->funcs->atomic_state_alloc) {
+		struct drm_atomic_state *state;
+
 		state = kzalloc(sizeof(*state), GFP_KERNEL);
 		if (!state)
 			return NULL;