net: stmmac: selftests: Fix sparse warning

Variable shall be __be16. Fix it.

Fixes: 091810db ("net: stmmac: Introduce selftests support")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c

@@ -114,7 +114,7 @@ static struct sk_buff *stmmac_test_get_udp_skb(struct stmmac_priv *priv,
 	}
 
 	if (attr->vlan) {
-		u16 *tag, *proto;
+		__be16 *tag, *proto;
 
 		if (!attr->remove_sa) {
 			tag = (void *)ehdr + ETH_HLEN;