Bluetooth: Send Ack after clear the SREJ list

As specified by Bluetooth 3.0 spec we shall send an acknowledgment using
the Send-Ack() after clear the SREJ list.

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>