drm/sti: code clean up

Purpose is to simplify the STI driver:
- remove layer structure
- consider video subdev as part of the compositor (like mixer subdev)
- remove useless STI_VID0 and STI_VID1 enum

Signed-off-by: Vincent Abriou <vincent.abriou@st.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>

drivers/gpu/drm/sti/sti_hdmi.c

@@ -588,7 +588,7 @@ static int sti_hdmi_connector_get_modes(struct drm_connector *connector)
 	return count;
 
 fail:
-	DRM_ERROR("Can not read HDMI EDID\n");
+	DRM_ERROR("Can't read HDMI EDID\n");
 	return 0;
 }