s390/net: use net core MTU range checking

ctcm:
- min_mtu = 576, max_mtu = 65527

netiucv:
- min_mtu = 576, max_mtu = 65535

qeth:
- min_mtu = 64, max_mtu = 65535

CC: netdev@vger.kernel.org
CC: linux-s390@vger.kernel.org
CC: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>