tty: Fix regressions in the char driver conversion

This forgot to update a field in the old char drivers. The fact nobody
has basically noticed (except one mxser user) rather suggests most of these
drivers could go into the bitbucket.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Andreas Pretzsch <apr@cn-eng.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>