exynos: fixes an incorrect header guard

in the exynos gpu driver where the preprocessor #ifndef/#define
variables were mismatched.
Signed-off-by: Ashley Towns <mail@ashleytowns.id.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/gpu/drm/exynos/exynos_drm_fb.h

@@ -12,7 +12,7 @@
  */
 
 #ifndef _EXYNOS_DRM_FB_H_
-#define _EXYNOS_DRM_FB_H
+#define _EXYNOS_DRM_FB_H_
 
 #include "exynos_drm_gem.h"