net: dsa: mxl862xx: implement VLAN functionality

Add VLAN support using both the Extended VLAN (EVLAN) engine and the
VLAN Filter (VF) engine in a hybrid architecture that allows a higher
number of VIDs than either engine could achieve alone.

The VLAN Filter engine handles per-port VID membership checks with
discard-unmatched semantics. The Extended VLAN engine handles PVID
insertion on ingress (via fixed catchall rules) and tag stripping on
egress (2 rules per untagged VID). Tagged-only VIDs need no EVLAN
egress rules at all, so they consume only a VF entry.

Both engines draw from shared 1024-entry hardware pools. The VF pool
is divided equally among user ports for VID membership, while the
EVLAN pool is partitioned into small fixed-size ingress blocks (7
entries of catchall rules per port) and fixed-size egress blocks for
tag stripping.

With 5 user ports this yields up to 204 VIDs per port (limited by VF),
of which up to 98 can be untagged (limited by EVLAN egress budget).
With 9 user ports the numbers are 113 total and 53 untagged.

Wire up .port_vlan_add, .port_vlan_del, and .port_vlan_filtering.
Reprogram all EVLAN rules when the PVID or filtering mode changes.
Detach blocks from the bridge port before freeing them on bridge leave
to satisfy the firmware's internal refcount.

Future optimizations could increase VID capacity by dynamically sizing
the egress EVLAN blocks based on actual per-port untagged VID counts
rather than worst-case pre-allocation, or by sharing EVLAN egress and
VLAN Filter blocks across ports with identical VID sets.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/9be29637675342b109a85fa08f5378800d9f7b78.1775581804.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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