tty: tty_port: Demote obvious abuse of kernel-doc formatting

tty: tty_port: Demote obvious abuse of kernel-doc formatting

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

 drivers/tty/tty_port.c:633: warning: Function parameter or member 'port' not described in 'tty_port_close'
 drivers/tty/tty_port.c:633: warning: Function parameter or member 'tty' not described in 'tty_port_close'
 drivers/tty/tty_port.c:633: warning: Function parameter or member 'filp' not described in 'tty_port_close'
 drivers/tty/tty_port.c:672: warning: Function parameter or member 'port' not described in 'tty_port_open'
 drivers/tty/tty_port.c:672: warning: Function parameter or member 'tty' not described in 'tty_port_open'
 drivers/tty/tty_port.c:672: warning: Function parameter or member 'filp' not described in 'tty_port_open'

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/20201104193549.4026187-7-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>