mlxsw: spectrum_switchdev: Implement mlxsw_sp_mc_mdb_entry_{init, fini}()

mlxsw: spectrum_switchdev: Implement mlxsw_sp_mc_mdb_entry_{init, fini}()

The next patches will convert MDB code to use PGT APIs. The change will
move the responsibility of allocating MID indexes and writing PGT
configurations to hardware to PGT code. As part of this change, most of the
MDB code will be changed and improved.

As a preparation for the above mentioned change, implement
mlxsw_sp_mc_mdb_entry_{init, fini}(). Currently, there is a function
__mlxsw_sp_mc_alloc(), which does not only allocate MID. In addition,
there is no an equivalent function to free the MID. When
mlxsw_sp_port_remove_from_mid() removes the last port, it handles MID
removal. Instead, add init() and fini() functions, which use PGT APIs.

The differences between the existing and the new functions are as follows:
1. Today MDB code does not update SMID when port is added/removed while
   multicast is disabled. It maintains a bitmap of ports and once multicast
   is enabled, it writes the entry to hardware. Instead, using PGT APIs,
   the entry will be updated also when multicast is disabled, but the
   mapping between {MAC, FID}->{MID} (is configured using SFD) will be
   updated according to multicast state. It means that SMID will be updated
   all the time and disable/enable multicast will impact only SFD
   configuration.

2. Today the allocation of MID index is done as part of
   mlxsw_sp_mc_write_mdb_entry(). The fact that the entry will be
   written in hardware all the time, moves the allocation of the index to
   be as part of the MDB entry initialization. PGT API is used for the
   allocation.

3. Today the update of multicast router ports is done as part of
   mlxsw_sp_mc_write_mdb_entry(). Instead, add functions to add/remove
   all multicast router ports when entry is first added or removed. When
   new multicast router port will be added/removed, the dedicated API will
   be used to add/remove it from the existing entries.

4. A list of ports will be stored per MDB entry instead of the exiting
   bitmap. The list will contain the multicast router ports and maintain
   reference counter per port.

Add mlxsw_sp_mdb_entry_write() which is almost identical to
mlxsw_sp_port_mdb_op(). Use more clear name and align the MID index to
bridge model using PGT API. The existing function will be removed in the
next patches.

Note that PGT APIs configure the firmware using SMID register, like the
driver already does today for MDB entries, so PGT APIs can be used also
using legacy bridge model.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>