serial: max3100: Extract to_max3100_port() helper macro

Instead of using container_of() explicitly, introduce a helper macro.
This saves a lot of lines of code.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240409144721.638326-8-andriy.shevchenko@linux.intel.com


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