fm10k: Implement PF <-> SM mailbox operations

This patch adds support for the mailbox that connects the PF to the Switch
Management entity.  This mailbox will pass TLV formatted messages between
the two entities by using a pair of shared ring buffers.

The primary use of the mailbox is to configure L2 forwarding addresses,
VLANs, and general resource allocation from the switch.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>