tty: serial: ifx6x60: Fix function documentation headers

tty: serial: ifx6x60: Fix function documentation headers

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

 drivers/tty/serial/ifx6x60.c:553: warning: Function parameter or member 'tty' not described in 'ifx_port_activate'
 drivers/tty/serial/ifx6x60.c:728: warning: Function parameter or member 't' not described in 'ifx_spi_io'
 drivers/tty/serial/ifx6x60.c:728: warning: Excess function parameter 'data' description in 'ifx_spi_io'

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Filip Aben <f.aben@option.com>
Cc: Joseph Barrow <d.barow@option.com>
Cc: Jan Dumon <j.dumon@option.com>
Cc: Russ Gorby <russ.gorby@intel.com>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-22-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>