octeontx2-af: CN20k mbox to support AF REQ/ACK functionality

octeontx2-af: CN20k mbox to support AF REQ/ACK functionality

This implementation uses separate trigger interrupts for request,
response MBOX messages against using trigger message data in CN10K.
This patch adds support for basic mbox implementation for CN20K
from AF side.

Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Link: https://patch.msgid.link/1749639716-13868-4-git-send-email-sbhatta@marvell.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>