staging: dgnc: Remove space before tabs

This patch fixes the warning of "Please, no space before tab" produced
by checkpatch.pl. The modified file: dgnc_tty.c

Signed-off-by: Dilek Uzulmez <dilekuzulmez@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>