ipv6: Make ipv6_mc_may_pull() return bool.

Consistent with how pskb_may_pull() also now does so.
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/addrconf.h

@@ -202,11 +202,11 @@ u32 ipv6_addr_label(struct net *net, const struct in6_addr *addr,
 /*
  *	multicast prototypes (mcast.c)
  */
-static inline int ipv6_mc_may_pull(struct sk_buff *skb,
-				   unsigned int len)
+static inline bool ipv6_mc_may_pull(struct sk_buff *skb,
+				    unsigned int len)
 {
 	if (skb_transport_offset(skb) + ipv6_transport_len(skb) < len)
-		return 0;
+		return false;
 
 	return pskb_may_pull(skb, len);
 }