tty: doc: Fix grammar in serial/tty

Correct spelling typos in serial/tty

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
1 file changed