mt76: connac: fix UC entry is being overwritten

Fix UC entry is being overwritten by BC entry

Tested-by: Deren Wu <deren.wu@mediatek.com>
Co-developed-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>