net: enetc: add MAC filtering for i.MX95 ENETC PF

The i.MX95 ENETC supports both MAC hash filter and MAC exact filter. MAC
hash filter is implenented through a 64-bit hash table to match against
the hashed addresses, PF and VFs each have two MAC hash tables, one is
for unicast and the other one is for multicast. But MAC exact filter is
shared between SIs (PF and VFs), each table entry contains a MAC address
that may be unicast or multicast and the entry also contains an SI bitmap
field that indicates for which SIs the entry is valid.

For i.MX95 ENETC, MAC exact filter only has 4 entries. According to the
observation of the system default network configuration, the MAC filter
will be configured with multiple multicast addresses, so MAC exact filter
does not have enough entries to implement multicast filtering. Therefore,
the current MAC exact filter is only used for unicast filtering. If the
number of unicast addresses exceeds 4, then MAC hash filter is used.

Note that both MAC hash filter and MAC exact filter can only be accessed
by PF, VFs can notify PF to set its corresponding MAC filter through the
mailbox mechanism of ENETC. But currently MAC filter is only added for
i.MX95 ENETC PF. The MAC filter support of ENETC VFs will be supported in
subsequent patches.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20250506080735.3444381-5-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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