liquidio: get rid of false alarm "Unknown cmd 27" in dmesg

Creating a macvtap interface with the liquidio VF driver as lower device
causes this alarming message to show up in dmesg:

    liquidio_link_ctrl_cmd_completion Unknown cmd 27

That's actually a false alarm because cmd 27 is the value of the macro
OCTNET_CMD_SET_UC_LIST which is known.  It's a control command sent from
host to NIC firmware to set the unicast MAC address list of the macvtap
lower device.

Make the false alarm go away by adding a case for OCTNET_CMD_SET_UC_LIST
in liquidio_link_ctrl_cmd_completion().

Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: Raghu Vatsavayi <raghu.vatsavayi@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>