Bluetooth: Return NOTIFY_DONE for hci_suspend_notifier

The original return is NOTIFY_STOP, but notifier_call_chain would stop
the future call for register_pm_notifier even registered on other Kernel
modules with the same priority which value is zero.

Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>