staging: dgnc: remove duplicated tty defines

The dgnc driver defined numerous TTY defines that the core kernel
already defines.  So just remove this duplication.

Cc: Lidza Louina <lidza.louina@gmail.com>
Cc: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>