fbdev: sh_mobile_lcdcfb: Don't use plain 0 as NULL pointer

This fixes a sparse warning.

Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/sh_mobile_lcdcfb.c

@@ -1227,7 +1227,7 @@ static void sh_mobile_lcdc_stop(struct sh_mobile_lcdc_priv *priv)
 		/* Free the MERAM cache. */
 		if (ch->cache) {
 			sh_mobile_meram_cache_free(priv->meram_dev, ch->cache);
-			ch->cache = 0;
+			ch->cache = NULL;
 		}
 
 	}