octeontx2-pf: Enable SRIOV and added VF mbox handling

Added 'sriov_configure' to enable/disable virtual functions (VFs).
Also added handling of mailbox messages from these VFs.

Admin function (AF) is the only one with all priviliges to configure
HW, alloc resources etc etc, PFs and it's VFs have to request AF
via mbox for all their needs. But unlike PFs, their VFs cannot
send a mbox request directly. A VF shares a mailbox region with
it's parent PF, so VF sends a mailbox msg to PF and then PF forwards
it to AF. Then AF after processing sends response to PF which it
again forwards to VF.

This patch adds support for this 'VF <=> PF <=> AF' mailbox
communication.

Signed-off-by: Tomasz Duszynski <tduszynski@marvell.com>
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Christina Jacob <cjacob@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>