RDMA/cma: Correct detection of SA Created MGID

RDMA CM treats AF_INET6 addresses that are either 0 or prefixed with
FF1x:A01B::/32 as MGIDs, but the detection for the prefix was buggy;
fix it up.
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/cma.c

@@ -2687,7 +2687,7 @@ static void cma_set_mgid(struct rdma_id_private *id_priv,
 	if (cma_any_addr(addr)) {
 		memset(mgid, 0, sizeof *mgid);
 	} else if ((addr->sa_family == AF_INET6) &&
-		   ((be32_to_cpu(sin6->sin6_addr.s6_addr32[0]) & 0xFF10A01B) ==
+		   ((be32_to_cpu(sin6->sin6_addr.s6_addr32[0]) & 0xFFF0FFFF) ==
 								 0xFF10A01B)) {
 		/* IPv6 address is an SA assigned MGID. */
 		memcpy(mgid, &sin6->sin6_addr, sizeof *mgid);