drm/ch7006: Stop using drm_crtc_force_disable

The correct way for legacy drivers to update properties that need to
do a full modeset, is to do a full modeset.

Note that we don't need to call the drm_mode_config_internal helper
because we're not changing any of the refcounted paramters.

v2: Fixup error handling (Ville). Since the old code didn't bother
I decided to just delete it instead of adding even more code for just
error handling.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181217194303.14397-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/i2c/ch7006_drv.c

@@ -359,10 +359,10 @@ static int ch7006_encoder_set_property(struct drm_encoder *encoder,
 	if (modes_changed) {
 		drm_helper_probe_single_connector_modes(connector, 0, 0);
 
-		/* Disable the crtc to ensure a full modeset is
-		 * performed whenever it's turned on again. */
 		if (crtc)
-			drm_crtc_force_disable(crtc);
+			drm_crtc_helper_set_mode(crtc, &crtc->mode,
+						 crtc->x, crtc->y,
+						 crtc->primary->fb);
 	}
 
 	return 0;