staging: dgnc: remove dead code in dgnc_tty_write()

Remove the dead code protected by in_user in dgnc_tty_write() because it
is set to 0 and never changed to 1 thus the code in ifs never gets
executed.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>