tty: tty_jobctrl: Add missing function parameter descriptions

tty: tty_jobctrl: Add missing function parameter descriptions

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

 drivers/tty/tty_jobctrl.c:32: warning: Function parameter or member 'sig' not described in '__tty_check_change'
 drivers/tty/tty_jobctrl.c:95: warning: Function parameter or member 'tty' not described in '__proc_set_tty'
 drivers/tty/tty_jobctrl.c:344: warning: Function parameter or member 'file' not described in 'tiocsctty'

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-8-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>