tty: fix kernel-doc for {start,stop}_tty

tty: fix kernel-doc for {start,stop}_tty

Commit f9e053dcfc02 (tty: Serialize tty flow control changes with
flow_lock) renamed start_tty to __start_tty and stop_tty to __stop_tty
and introduced new start_tty and stop_tty. But it left kernel-doc
comments on the old locations:
 tty_io.c:785: warning: expecting prototype for stop_tty(). Prototype was for __stop_tty() instead
 tty_io.c:816: warning: expecting prototype for start_tty(). Prototype was for __start_tty() instead

Fix that by moving the comments to appropriate locations.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210519072153.3859-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>