tty: add ASYNC_SPLIT_TERMIOS to deprecation mask

Callout devices are long-gone, but the ASYNC_SPLIT_TERMIOS flag was
never added to the deprecation mask.

Add it so that a warning is printed if it is ever used.

Fixes: 8a8ae62f ("tty: warn on deprecated serial flags")
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210407095208.31838-7-johan@kernel.org


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