Bluetooth: Don't disable tasklets to call hdev->notify()

It's pointless, we aren't protecting anything since btusb_notify()
schedules a work to run, then all it operation happens without protection.
If protection is really needed here, we will fix it further.

Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>