netlink: fix unaligned access in nla_get_be64()

This patch fixes a unaligned access in nla_get_be64() that was
introduced by myself in a17c859849.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netlink.h

@@ -945,7 +945,11 @@ static inline u64 nla_get_u64(const struct nlattr *nla)
  */
 static inline __be64 nla_get_be64(const struct nlattr *nla)
 {
-	return *(__be64 *) nla_data(nla);
+	__be64 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**