tty: tty_port: Fix coding style issues of block comments

Fix coding style issues of block comments, reported by checkpatch.pl.
Besides, add a period at the end of the sentenses.

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Link: https://lore.kernel.org/r/1620811585-18582-18-git-send-email-tanxiaofei@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>