ip xfrm state: Allow different selector family

My previous commit introduced a patch to allow for states with different
ip address families for selector and id. The must have somehow been a
mixup of the patch I tested and the one I send, so the patch sent breaks
the iproute2 build. This patch fixes this. My apologies.
Signed-off-by: Thomas Egerer <hakke_007@gmx.de>

ip/xfrm_state.c

@@ -296,7 +296,7 @@ static int xfrm_state_modify(int cmd, unsigned flags, int argc, char **argv)
 			NEXT_ARG();
 			preferred_family = AF_UNSPEC;
 			xfrm_selector_parse(&req.xsinfo.sel, &argc, &argv);
-			preferred_family = req.xsinfo.sel;
+			preferred_family = req.xsinfo.sel.family;
 		} else if (strcmp(*argv, "limit") == 0) {
 			NEXT_ARG();
 			xfrm_lifetime_cfg_parse(&req.xsinfo.lft, &argc, &argv);