s390/qeth: support early setup for z/VM NICs

s390/qeth: support early setup for z/VM NICs

BugLink: http://bugs.launchpad.net/bugs/1747639
The transport mode that a z/VM NIC is configured in, must match the
hypervisor-internal network which the NIC is coupled to.

To get this right automatically, have qeth issue a diag26c hypervisor call
that provides all sorts of information for a specific VNIC.
With z/VM update VM65918, this also includes the VNIC's required
transport mode.

Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 615dff228368109ce18b628d6bd1b01ad6ef2f74)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>