wifi: rtw88: Skip high queue in hci_flush

The flush period may not always intersect with DTIM and when that
happens, an error log "timed out to flush pci TX ring[6]" is shown.
Bypass this since hardware will do proper transmission on the next
DTIM period for broadcast/multicast packets in high queue.

Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230616125540.36877-4-pkshih@realtek.com