liquidio: fix VF incorrectly indicating that it successfully set its VLAN

For security reasons, NIC firmware does not allow VF to set its VLAN if PF
set it already.  Firmware allows VF to set its VLAN if PF did not set it.
After the VF instructs the firmware to set the VLAN, VF always indicates
(via return 0) that the operation is successful--even for the times when it
isn't.

Put in a mechanism for the VF's set VLAN function to receive the firmware
response code, then make that function return -EPERM if the firmware
forbids the operation.

Make that mechanism available for other functions that may, in the future,
be interested in receiving the response code from the firmware.  That
mechanism involves adding new fields to struct octnic_ctrl_pkt, so make all
users of struct octnic_ctrl_pkt initialize the struct to zero before using
it; otherwise, the mechanism might act on uninitialized garbage.

Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: Derek Chickles <derek.chickles@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>