af_key: make use of BUG_ON macro

fix below warnings reported by coccicheck

net/key/af_key.c:932:2-5: WARNING: Use BUG_ON instead of if condition
followed by BUG.
net/key/af_key.c:948:2-5: WARNING: Use BUG_ON instead of if condition
followed by BUG.
Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/key/af_key.c

@@ -928,8 +928,7 @@ static struct sk_buff *__pfkey_xfrm_state2msg(const struct xfrm_state *x,
 		pfkey_sockaddr_fill(&x->props.saddr, 0,
 				    (struct sockaddr *) (addr + 1),
 				    x->props.family);
-	if (!addr->sadb_address_prefixlen)
-		BUG();
+	BUG_ON(!addr->sadb_address_prefixlen);
 
 	/* dst address */
 	addr = skb_put(skb, sizeof(struct sadb_address) + sockaddr_size);
@@ -944,8 +943,7 @@ static struct sk_buff *__pfkey_xfrm_state2msg(const struct xfrm_state *x,
 		pfkey_sockaddr_fill(&x->id.daddr, 0,
 				    (struct sockaddr *) (addr + 1),
 				    x->props.family);
-	if (!addr->sadb_address_prefixlen)
-		BUG();
+	BUG_ON(!addr->sadb_address_prefixlen);
 
 	if (!xfrm_addr_equal(&x->sel.saddr, &x->props.saddr,
 			     x->props.family)) {