drm: vmwgfx: Remove unneeded CRTC .prepare() helper operation

The CRTC .prepare() helper operation is part of the legacy helpers and
is deprecated in favour of the .disable() helper operation. As the
vmwgfx driver provides a .disable() helper operation, and as the
.prepare() helper operation implementation is empty, we can remove it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170627211621.27767-5-laurent.pinchart+renesas@ideasonboard.com

drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c

@@ -202,18 +202,6 @@ static void vmw_ldu_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 }
 
-/**
- * vmw_ldu_crtc_helper_prepare - Noop
- *
- * @crtc: CRTC associated with the new screen
- *
- * Prepares the CRTC for a mode set, but we don't need to do anything here.
- *
- */
-static void vmw_ldu_crtc_helper_prepare(struct drm_crtc *crtc)
-{
-}
-
 /**
  * vmw_ldu_crtc_helper_commit - Noop
  *
@@ -388,7 +376,6 @@ drm_plane_helper_funcs vmw_ldu_primary_plane_helper_funcs = {
 };
 
 static const struct drm_crtc_helper_funcs vmw_ldu_crtc_helper_funcs = {
-	.prepare = vmw_ldu_crtc_helper_prepare,
 	.commit = vmw_ldu_crtc_helper_commit,
 	.disable = vmw_ldu_crtc_helper_disable,
 	.mode_set_nofb = vmw_ldu_crtc_mode_set_nofb,