6lowpan: ndisc: add missing 802.15.4 only check

This patch adds a missing check to handle short address parsing for
802.15.4 6LoWPAN only.

Signed-off-by: Alexander Aring <aar@pengutronix.de>
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/6lowpan/ndisc.c

@@ -47,6 +47,9 @@ static int lowpan_ndisc_parse_options(const struct net_device *dev,
 				      struct nd_opt_hdr *nd_opt,
 				      struct ndisc_options *ndopts)
 {
+	if (!lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154))
+		return 0;
+
 	switch (nd_opt->nd_opt_type) {
 	case ND_OPT_SOURCE_LL_ADDR:
 	case ND_OPT_TARGET_LL_ADDR: