serial: 8250: use serial_port_in/out() helpers

There are serial_port_in/out() helpers to be used instead of direct
p->serial_in/out(). Use them in various 8250 drivers.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

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[v2]
* Use serial_port_in/out() and not serial_in/out() [Andy]

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> # 8250_dw
Link: https://lore.kernel.org/r/20250317070046.24386-28-jirislaby@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>