Bluetooth: Remove the cmd timeout count in btusb

Remove the cmd timeout count in btusb since we only ever allow one
command in flight at a time. We should always reset after a single
command times out.

Signed-off-by: Hsin-chen Chuang <chharry@chromium.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>