IB/core: Fix endianness annotation in rdma_is_multicast_addr()

Since ipv4_addr is a big endian 32-bit number, annotate it as such.

Fixes: commit be1d325a3358 ("IB/core: Set RoCEv2 MGID according to spec")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

include/rdma/ib_addr.h

@@ -305,12 +305,12 @@ static inline void rdma_get_ll_mac(struct in6_addr *addr, u8 *mac)
 
 static inline int rdma_is_multicast_addr(struct in6_addr *addr)
 {
-	u32 ipv4_addr;
+	__be32 ipv4_addr;
 
 	if (addr->s6_addr[0] == 0xff)
 		return 1;
 
-	memcpy(&ipv4_addr, addr->s6_addr + 12, 4);
+	ipv4_addr = addr->s6_addr32[3];
 	return (ipv6_addr_v4mapped(addr) && ipv4_is_multicast(ipv4_addr));
 }