USB: cdc-acm: use CDC serial-state defines

Use the new CDC serial-state defines.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20220725075841.1187-5-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>