staging: dgrp: remove TIOCGSOFTCAR and TIOCSSOFTCAR handling

The TIOCGSOFTCAR and TIOCSSOFTCAR ioctls are handled by the tty layer
so the dgrp driver shouldn't try to deal with them itself.

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>