tty: pty: Provide descriptions for the 'file' parameters

Fixes the following W=1 kernel build warning(s):

 drivers/tty/pty.c:710: warning: Function parameter or member 'file' not described in 'ptm_unix98_lookup'
 drivers/tty/pty.c:726: warning: Function parameter or member 'file' not described in 'pts_unix98_lookup'

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: "C. Scott Ananian" <cananian@alumni.princeton.edu>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-17-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/pty.c

@@ -699,6 +699,7 @@ static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 /**
  *	ptm_unix98_lookup	-	find a pty master
  *	@driver: ptm driver
+ *	@file: unused
  *	@idx: tty index
  *
  *	Look up a pty master device. Called under the tty_mutex for now.
@@ -715,6 +716,7 @@ static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 /**
  *	pts_unix98_lookup	-	find a pty slave
  *	@driver: pts driver
+ *	@file: file pointer to tty
  *	@idx: tty index
  *
  *	Look up a pty master device. Called under the tty_mutex for now.