drm/gma500: remove an unneeded NULL check

"connector" is the list iterator and it can't be NULL.  It causes a
static checker warning because we dereference the iterator to get the
next item in the list.  Let's remove this check.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170628124100.3pw2gyitsfopaib5@mwanda

drivers/gpu/drm/gma500/mdfld_intel_display.c

@@ -737,11 +737,7 @@ static int mdfld_crtc_mode_set(struct drm_crtc *crtc,
 					sizeof(struct drm_display_mode));
 
 	list_for_each_entry(connector, &mode_config->connector_list, head) {
-		if (!connector)
-			continue;
-
 		encoder = connector->encoder;
-
 		if (!encoder)
 			continue;