serial: 8250_fintek: Set IRQ Mode when port probed

Set IRQ Mode when port probed in probe_setup_port()

It should hold the IO port premission via fintek_8250_enter_key() and
release via fintek_8250_exit_key() when we configure the SuperIO.

This patch will move all SuperIO configure operations to
probe_setup_port() to reduce fintek_8250_enter_key() and
fintek_8250_exit_key() usage.

Suggested-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>