ibmvnic: Convert vnic server reported statistics to cpu endian

The vnic server reports the statistics buffer in big endian format and must
be converted to cpu endian in order to be displayed correctly on little
endian lpars.

Signed-off-by: John Allen <jallen@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>