mt76: mt7915: refresh repeater entry MAC address when setting BSSID

When disassociating and clearing the BSSID of a repeater entry used by a client
mode interface, the corresponding MAC address entry can get lost too, causing
the client interface to not be able to associate anymore.
Fix this by also refreshing the MAC address when setting the BSSID

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