net: dsa: mv88e6xxx: Add number of MACs in the ATU

[ Upstream commit d9ea56206c4df77175321874544eb4ca48c0bac8 ]

For each supported switch, add an entry to the info structure for the
number of MACs which can be stored in the ATU. This will later be used
to export the ATU as a devlink resource, and indicate its occupancy,
how full the ATU is.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: b9a61c20179f ("net: dsa: mv88e6xxx: Fix number of databases for 88E6141 / 88E6341")
Signed-off-by: Sasha Levin <sashal@kernel.org>