Bluetooth: btusb: Fix suspend issue for Realtek devices

From the perspective of controller, global suspend means there is no
SET_FEATURE (DEVICE_REMOTE_WAKEUP) and controller would drop the
firmware. It would consume less power. So we should not send this kind
of SET_FEATURE when host goes to suspend state.
Otherwise, when making device enter selective suspend, host should send
SET_FEATURE to make sure the firmware remains.

Signed-off-by: Alex Lu <alex_lu@realsil.com.cn>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>