ibmvnic: Fix ibmvnic_change_mac_addr struct format

The ibmvnic_change_mac_addr struct alignment was not matching the defined
format in PAPR+, it had the reserved and return code fields swapped. As a
consequence, the CHANGE_MAC_ADDR_RSP commands were being improperly handled
and executed even when the operation wasn't successfully completed by the
system firmware.

Also changing the endianness of the debug message to make it easier to
parse the CRQ content.

Signed-off-by: Murilo Fossa Vicentini <muvic@linux.vnet.ibm.com>
Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>