Bluetooth: Support case with F bit set under WAIT_F state.

On receipt of a F=1 under WAIT_F state ERTM shall stop monitor timer and
start retransmission timer (if there are unacked frames).

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>