serial: port: Make ->iotype validation global in __uart_read_properties()

In order to make code robust against potential changes in the future
move ->iotype validation outside of switch in __uart_read_properties().
If any code will be added in between that might leave the ->iotype value
unknown the validation catches this up.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250124161530.398361-4-andriy.shevchenko@linux.intel.com


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