IB/addr: Correct CONFIG_IPv6 to CONFIG_IPV6

Correct misspelled "CONFIG_IPv6" that was introduced in commit
d14714df ("IB/addr: Fix IPv6 routing lookup").  The config variable
should be all uppercase.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

[ This was my fault when I munged the original patch.  - Roland ]
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/cma.c

@@ -2083,7 +2083,7 @@ static int cma_get_port(struct rdma_id_private *id_priv)
 static int cma_check_linklocal(struct rdma_dev_addr *dev_addr,
 			       struct sockaddr *addr)
 {
-#if defined(CONFIG_IPv6) || defined(CONFIG_IPV6_MODULE)
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 	struct sockaddr_in6 *sin6;
 
 	if (addr->sa_family != AF_INET6)