drm/crtc_helper/set_config: Remove redundant handling when set->fb is NULL

We've done sanity NULL pointer check on set->fb at the beginning of
drm_crtc_helper_set_config() and bailed out if necessary, thus any later on
check or case handling is redundant.
Signed-off-by: Liu Ying <gnuiyl@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452751210-19216-1-git-send-email-gnuiyl@gmail.comSigned-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc_helper.c

@@ -578,8 +578,6 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
 		if (set->crtc->primary->fb == NULL) {
 			DRM_DEBUG_KMS("crtc has no fb, full mode set\n");
 			mode_changed = true;
-		} else if (set->fb == NULL) {
-			mode_changed = true;
 		} else if (set->fb->pixel_format !=
 			   set->crtc->primary->fb->pixel_format) {
 			mode_changed = true;