wifi: mt76: mt7915: ensure that only one sta entry is active per mac address

When a client is roaming to a different AP interface, a duplicate wtbl entry
can be created. This can lead to lost packets or aggregation issues until
the old entry expires.
In order to fix this issue, delete any conflicting entries from WTBL
whenever a station is authorized.

Link: https://patch.msgid.link/20241230194202.95065-9-nbd@nbd.name


Signed-off-by: Felix Fietkau <nbd@nbd.name>