Bluetooth: Replace send_monitor_event with queue_monitor_skb

The send_monitor_event function is essentially the same as the newly
introduced queue_monitor_skb. So instead of having duplicated code,
replace send_monitor_event with queue_monitor_skb.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>