drm/mxsfb: Add pm_runtime calls to pipe_enable/disable

Adding lcdif nodes to a power domain currently results in
black/corrupted screens or hangs because power is not correctly enabled
when required.

Ensure power is on when display is active by adding
pm_runtime_get/put_sync to mxsfb_pipe_enable/disable.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/ee88148399c63494cda4129b05444b0ac331b7a7.1537191359.git.leonard.crestez@nxp.com

drivers/gpu/drm/mxsfb/mxsfb_drv.c

@@ -103,7 +103,9 @@ static void mxsfb_pipe_enable(struct drm_simple_display_pipe *pipe,
 			      struct drm_plane_state *plane_state)
 {
 	struct mxsfb_drm_private *mxsfb = drm_pipe_to_mxsfb_drm_private(pipe);
+	struct drm_device *drm = pipe->plane.dev;
 
+	pm_runtime_get_sync(drm->dev);
 	drm_panel_prepare(mxsfb->panel);
 	mxsfb_crtc_enable(mxsfb);
 	drm_panel_enable(mxsfb->panel);
@@ -112,10 +114,12 @@ static void mxsfb_pipe_enable(struct drm_simple_display_pipe *pipe,
 static void mxsfb_pipe_disable(struct drm_simple_display_pipe *pipe)
 {
 	struct mxsfb_drm_private *mxsfb = drm_pipe_to_mxsfb_drm_private(pipe);
+	struct drm_device *drm = pipe->plane.dev;
 
 	drm_panel_disable(mxsfb->panel);
 	mxsfb_crtc_disable(mxsfb);
 	drm_panel_unprepare(mxsfb->panel);
+	pm_runtime_put_sync(drm->dev);
 }
 
 static void mxsfb_pipe_update(struct drm_simple_display_pipe *pipe,