[fc] Hold reference to peers and ULPs while calling fc_link_examine()

Allow link examination methods to safely assume that their
self-reference remains valid for the duration of the method call.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/fc.c

 	fc_link_up ( &port->link );
 
 	/* Notify peers of link state change */
-	list_for_each_entry_safe ( peer, tmp, &fc_peers, list )
+	list_for_each_entry_safe ( peer, tmp, &fc_peers, list ) {
+		fc_peer_get ( peer );
 		fc_link_examine ( &peer->link );
+		fc_peer_put ( peer );
+	}
 
 	return 0;
 }
 	fc_link_err ( &port->link, rc );
 
 	/* Notify peers of link state change */
-	list_for_each_entry_safe ( peer, tmp, &fc_peers, list )
+	list_for_each_entry_safe ( peer, tmp, &fc_peers, list ) {
+		fc_peer_get ( peer );
 		fc_link_examine ( &peer->link );
+		fc_peer_put ( peer );
+	}
 }
 
 /**
 	fc_link_up ( &peer->link );
 
 	/* Notify ULPs of link state change */
-	list_for_each_entry_safe ( ulp, tmp, &peer->ulps, list )
+	list_for_each_entry_safe ( ulp, tmp, &peer->ulps, list ) {
+		fc_ulp_get ( ulp );
 		fc_link_examine ( &ulp->link );
+		fc_ulp_put ( ulp );
+	}
 
 	return 0;
 }
 	fc_link_err ( &peer->link, rc );
 
 	/* Notify ULPs of link state change */
-	list_for_each_entry_safe ( ulp, tmp, &peer->ulps, list )
+	list_for_each_entry_safe ( ulp, tmp, &peer->ulps, list ) {
+		fc_ulp_get ( ulp );
 		fc_link_examine ( &ulp->link );
+		fc_ulp_put ( ulp );
+	}
 
 	/* Close peer if there are no active users */
 	if ( peer->usage == 0 )