Bluetooth: btusb: Implement hdev->prevent_wake

Implement the prevent_wake hook by checking device_may_wakeup on the usb
interface. This prevents the Bluetooth core from enabling scanning when
the device isn't expected to wake from suspend.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Alain Michaud <alainm@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>