drm/sti: rename files and functions

replace all "sti_drm_" occurences by "sti_"

Signed-off-by: Vincent Abriou <vincent.abriou@st.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
diff --git a/drivers/gpu/drm/sti/sti_mixer.h b/drivers/gpu/drm/sti/sti_mixer.h
index 9d51eac..2f69b00 100644
--- a/drivers/gpu/drm/sti/sti_mixer.h
+++ b/drivers/gpu/drm/sti/sti_mixer.h
@@ -11,7 +11,7 @@
 
 #include <drm/drmP.h>
 
-#include "sti_drm_plane.h"
+#include "sti_plane.h"
 
 #define to_sti_mixer(x) container_of(x, struct sti_mixer, drm_crtc)