octeontx2-af: CGX Rx/Tx enable/disable mbox handlers

Added new mailbox msgs for RVU PF/VFs to request AF
to enable/disable their mapped CGX::LMAC Rx & Tx.

Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Linu Cherian <lcherian@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>