net: dsa: b53: Implement ARL add/del/dump operations

Adds support for FDB add/delete/dump using the ARL read/write logic and
the ARL search logic for faster dumps. The code is made flexible enough
it could support devices with a different register layout like BCM5325
and BCM5365 which have fewer number of entries or pack values into a
single 64 bits register.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>