ip link: Remove unnecessary device checking

The real checking is performed later in iplink_modify(..) func which
checks device existence if NLM_F_CREATE flag is set.

Also it fixes the case when impossible to add veth link which was
caused by 9a02651a87 (ip: check for missing dev arg when doing VF rate)
because these devices are not exist yet.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

ip/iplink.c

@@ -593,8 +593,6 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req,
 				duparg2("dev", *argv);
 			*dev = *argv;
 			dev_index = ll_name_to_index(*dev);
-			if (dev_index == 0)
-				invarg("Unknown device", *argv);
 		}
 		argc--; argv++;
 	}