mlxsw: spectrum_router: Add RIF MAC profiles support

Currently, mlxsw enforces that all the router interfaces (RIFs) have the
same MAC prefix.

Relax this limitation by using RIF MAC profiles. Each profile is
associated with a particular MAC prefix and multiple RIFs can use the
same profile. Therefore, the number of possible MAC prefixes is no
longer one, but the number of profiles supported by the device.

Store the profiles in an IDR and reference count them according to the
number of RIFs using them.

Associate a RIF with a profile when the RIF is created and remove the
association when the RIF is deleted.

Change the association following 'NETDEV_CHANGEADDR' events, except when
only one RIF is using the profile. In which case, change the MAC prefix
of the profile itself instead of associating the RIF with a new profile.

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>