octeontx2-af: optimize cpt pf identification

commit b0fb3897ca4c971af827518e9441f2721fc1209c from
git@git.assembla.com:cavium/WindRiver.linux.git

Optimize CPT PF identification in mbox handling for faster
mbox response by doing it at AF driver probe instead of
every mbox message.

Change-Id: Id7143f70f8ead3b1e5005a156f5933084c8f8d42
Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/65153


Reviewed-by: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
Reviewed-by: Tejasree Kondoj <ktejasree@marvell.com>
Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>