mlxsw: spectrum: Implement common FID core

mlxsw: spectrum: Implement common FID core

The device supports three types of FIDs. 802.1Q and 802.1D FIDs for
VLAN-aware and VLAN-unaware bridges (respectively) and rFIDs to
transport packets to the router block.

The different users (e.g., bridge, router, ACLs) of the FIDs
infrastructure need not know about the internal FIDs implementation and
can therefore interact with it using a restricted set of exported
functions.

By encapsulating the entire FID logic and hiding it from the rest of the
driver we get a code base that it much simpler and easier to work with
and extend.

For example, in the current Spectrum ASIC only 802.1D FIDs can be
assigned a VNI, but future ASICs will also support 802.1Q FIDs. With
this patch in place, support for future ASICs can be easily added by
implementing a new FID operations according to their capabilities.

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