According to reference guides mt7530 (mt7620) and mt7531:

NOTE: When IVL is reset, MAC[47:0] and FID[2:0] will be used to
read/write the address table. When IVL is set, MAC[47:0] and CVID[11:0]
will be used to read/write the address table.

Since the function only fills in CVID and no FID, we need to set the
IVL bit. The existing code does not set it.

This is a fix for the issue I dropped here earlier:

http://lists.infradead.org/pipermail/linux-mediatek/2021-June/025697.html

With this patch, it is now possible to delete the 'self' fdb entry
manually. However, wifi roaming still has the same issue, the entry
does not get deleted automatically. Wifi roaming also needs a fix
somewhere else to function correctly in combination with vlan.
Signed-off-by: Eric Woudstra <ericwouds@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>