veth: remove unneeded ifname code from veth_newlink()

The code is not needed because tb[IFLA_IFNAME] is already
processed in rtnl_newlink(). Remove this redundancy.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>