wifi: mt76: fix tx packet loss when scanning on DBDC

When queueing packets, only the MT76_RESET flag of the primary PHY
is checked. If the primary PHY is scanning or changing channels, this can
lead to packet loss for tx on the second PHY.
Fix this by passing the phy to the .tx_queue_skb op and using it to check
the correct flag.

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