drm/i915: copy&paste drm_crtc_helper_set_mode

Together with the static helper functions drm_crtc_prepare_encoders
and drm_encoder_disable (which will be simplified in the next patch,
but for now are 1:1 copies). Again, no changes beside new names for
these functions.

Also call our new set_mode instead of the crtc helper one now in all
the places we've done so far.

v2: Call the function just intel_set_mode to better differentia it
from intel_crtc_mode_set which really only does the ->mode_set step of
the entire modeset sequence on one crtc. Whereas this function does
the global change.

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -2312,9 +2312,8 @@ intel_dp_set_property(struct drm_connector *connector,
 done:
 	if (intel_dp->base.base.crtc) {
 		struct drm_crtc *crtc = intel_dp->base.base.crtc;
-		drm_crtc_helper_set_mode(crtc, &crtc->mode,
-					 crtc->x, crtc->y,
-					 crtc->fb);
+		intel_set_mode(crtc, &crtc->mode,
+			       crtc->x, crtc->y, crtc->fb);
 	}
 
 	return 0;