Add support for Multi-Physical Function Switch, MPFS, in mlx5en.

Add support for Multi-Physical Function Switch, MPFS, in mlx5en.

MPFS is a logical switch in the Mellanox device which forward packets
based on a hardware driven L2 address table, to one or more physical-
or virtual- functions. The physical- or virtual- function is required
to tell the MPFS by using the MPFS firmware commands, which unicast
MAC addresses it is requesting from the physical port's traffic.
Broadcast and multicast traffic however, is copied to all listening
physical- and virtual- functions and does not need a rule in the MPFS
switching table.

Linux commit:	eeb66cdb682678bfd1f02a4547e3649b38ffea7e
MFC after:	3 days
Sponsored by:	Mellanox Technologies