tty: tty_io: Fix an issue of code indent for conditional statements

Fix an issue of code indent for conditional statements,reported by
checkpatch.pl.
Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Link: https://lore.kernel.org/r/1620811585-18582-13-git-send-email-tanxiaofei@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>