fix deps so xorg can once again be selected

package/xorg/Config.in

@@ -2,8 +2,8 @@ config BR2_PACKAGE_XORG
 	bool "X.org X Window System"
 	default n
 	depends !BR2_PACKAGE_TINYX
-	depends BR2_PACKAGE_ZLIB
-	depends BR2_PACKAGE_LIBPNG
+	select BR2_PACKAGE_ZLIB
+	select BR2_PACKAGE_LIBPNG
 	help
 	  The official X Window system and server.