ibmvnic: Report actual backing device speed and duplex values

The ibmvnic driver currently reports a fixed value for both speed and
duplex settings regardless of the actual backing device that is being
used. By adding support to the QUERY_PHYS_PARMS command defined by the
PAPR+ we can query the current physical port state and report the proper
values for these feilds.

Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Murilo Fossa Vicentini <muvic@linux.ibm.com>
Reviewed-by: Mauro S. M. Rodrigues <maurosr@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>