serial: port: Assign ->iotype correctly when ->iobase is set

Currently the ->iotype is always assigned to the UPIO_MEM when
the respective property is not found. However, this will not
support the cases when user wants to have UPIO_PORT to be set
or preserved.  Support this scenario by checking ->iobase value
and default the ->iotype respectively.

Fixes: 1117a6fd ("serial: 8250_of: Switch to use uart_read_port_properties()")
Fixes: e894b600 ("serial: port: Introduce a common helper to read properties")
Cc: stable <stable@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250124161530.398361-2-andriy.shevchenko@linux.intel.com


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