wifi: mt76: mt7996: Fix tx-queues initialization for second phy on mt7996

wifi: mt76: mt7996: Fix tx-queues initialization for second phy on mt7996

Fix the second phy tx queue initialization if hif device is not
available for MT7990 chipset.

Fixes: 83eafc9251d6d ("wifi: mt76: mt7996: add wed tx support")
Co-developed-by: Sujuan Chen <sujuan.chen@mediatek.com>
Signed-off-by: Sujuan Chen <sujuan.chen@mediatek.com>
Co-developed-by: Benjamin Lin <benjamin-jw.lin@mediatek.com>
Signed-off-by: Benjamin Lin <benjamin-jw.lin@mediatek.com>
Co-developed-by: Rex Lu <rex.lu@mediatek.com>
Signed-off-by: Rex Lu <rex.lu@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250909-mt7996-rro-rework-v5-8-7d66f6eb7795@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>