mlxsw: spectrum: Add initial support for Spectrum ASIC

Add support for new generation Mellanox Spectrum ASIC, 10/25/40/50 and
100Gb/s Ethernet Switch.

The initial driver implements bridge forwarding offload including
bridge internal VLAN support, FDB static entries, FDB learning and
HW ageing including their setup.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Elad Raz <eladr@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>