eth: fbnic: Allocate core device specific structures and devlink interface

At the core of the fbnic device will be the devlink interface. This
interface will eventually provide basic functionality in the event that
there are any issues with the network interface.

Add support for allocating the MSI-X vectors and setting up the BAR
mapping. With this we can start enabling various subsystems and start
brining up additional interfaces such the AXI fabric and the firmware
mailbox.

Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://patch.msgid.link/172079936012.1778861.4670986685222676467.stgit@ahduyck-xeon-server.home.arpa


Signed-off-by: Jakub Kicinski <kuba@kernel.org>