octeontx2-af: Configure AF VFs to talk over LBK channels

Configure AF VFs such that they are able to talk over consecutive
loopback channels.

If 8 VFs are attached to AF then communication will work as below:

TX      RX
lbk0 -> lbk1
lbk1 -> lbk0

lbk2 -> lbk3
lbk3 -> lbk2

lbk4 -> lbk5
lbk5 -> lbk4

lbk6 -> lbk7
lbk7 -> lbk6

Signed-off-by: Tomasz Duszynski <tduszynski@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>