wifi: rtl8xxxu: Select correct queue for beacon frames

Use the special beacon queue for beacon frames instead of the management
frame queue. They will be put in a special area called reserved page and
send out periodically when in AP mode.

Signed-off-by: Martin Kaistra <martin.kaistra@linutronix.de>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230428150833.218605-3-martin.kaistra@linutronix.de