RDMA/qedr: fix build error without ipv6

When CONFIG_IPV6 disabled, we run into a link error:

drivers/infiniband/hw/qedr/qedr_iw_cm.o: In function `qedr_addr6_resolve.isra.3':
qedr_iw_cm.c:(.text+0x4e0): undefined reference to `ip6_route_output_flags'

The ipv6 handling code is obviously not needed here, so this
adds a compile-time check for the Kconfig symbol in all three
places in the code that decide between ipv4 and ipv6.

We don't have to worry about a link error wtih QEDR=y/IPV6=m, as
that configuration is already prohibited by CONFIG_INFINIBAND
depending on "m || IPV6 != m".

Fixes: e411e0587e0d ("RDMA/qedr: Add iWARP connection management functions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michal Kalderon <michal.kalderon@cavium.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/qedr/qedr_iw_cm.c

@@ -98,7 +98,8 @@ qedr_iw_mpa_request(void *context, struct qed_iwarp_cm_event_params *params)
 	event.event = IW_CM_EVENT_CONNECT_REQUEST;
 	event.status = params->status;
 
-	if (params->cm_info->ip_version == QED_TCP_IPV4)
+	if (!IS_ENABLED(CONFIG_IPV6) ||
+	    params->cm_info->ip_version == QED_TCP_IPV4)
 		qedr_fill_sockaddr4(params->cm_info, &event);
 	else
 		qedr_fill_sockaddr6(params->cm_info, &event);
@@ -522,7 +523,8 @@ int qedr_iw_connect(struct iw_cm_id *cm_id, struct iw_cm_conn_param *conn_param)
 	memset(cm_info->local_ip, 0, sizeof(cm_info->local_ip));
 	memset(cm_info->remote_ip, 0, sizeof(cm_info->remote_ip));
 
-	if (cm_id->remote_addr.ss_family == AF_INET) {
+	if (!IS_ENABLED(CONFIG_IPV6) ||
+	    cm_id->remote_addr.ss_family == AF_INET) {
 		cm_info->ip_version = QED_TCP_IPV4;
 
 		cm_info->remote_ip[0] = ntohl(raddr->sin_addr.s_addr);
@@ -616,7 +618,8 @@ int qedr_iw_create_listen(struct iw_cm_id *cm_id, int backlog)
 	iparams.event_cb = qedr_iw_event_handler;
 	iparams.max_backlog = backlog;
 
-	if (cm_id->local_addr.ss_family == AF_INET) {
+	if (!IS_ENABLED(CONFIG_IPV6) ||
+	    cm_id->local_addr.ss_family == AF_INET) {
 		iparams.ip_version = QED_TCP_IPV4;
 		memset(iparams.ip_addr, 0, sizeof(iparams.ip_addr));