package/rtl8189es: disable -Werror to fix build failure

Fixes:
http://autobuild.buildroot.net/results/349893c66fcfbbf0e0e10285299581894254c941/

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/rtl8189es/rtl8189es.mk

@@ -11,7 +11,8 @@ RTL8189ES_LICENSE = GPL-2.0
 RTL8189ES_MODULE_MAKE_OPTS = \
 	CONFIG_RTL8189ES=m \
 	KVER=$(LINUX_VERSION_PROBED) \
-	KSRC=$(LINUX_DIR)
+	KSRC=$(LINUX_DIR) \
+	USER_EXTRA_CFLAGS="-Wno-error"
 
 define RTL8189ES_LINUX_CONFIG_FIXUPS
 	$(call KCONFIG_ENABLE_OPT,CONFIG_NET)