Bluetooth: hci_qca: Stop IBS timer during BT OFF

The IBS timers are not stopped properly once BT OFF is triggered.
we could see IBS commands being sent along with version command,
so stopped IBS timers while Bluetooth is off.

Fixes: 3e4be65e ("Bluetooth: hci_qca: Add poweroff support during hci down for wcn3990")
Signed-off-by: Panicker Harish <quic_pharish@quicinc.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>