Staging: gdm724x: tty: Remove unused macro 'gdm_tty_send_control'.

Remove the macro 'gdm_tty_send_control' which adds unnecessary complexity,
is unused, and has arguments that could mistakenly be evaluated multiple
times.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>