tty: tty_io: Remove spaces before tabs

Remove spaces before tabs following the advice of checkpatch.pl.
Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Link: https://lore.kernel.org/r/1620811585-18582-7-git-send-email-tanxiaofei@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>