gpio: mlxbf2: Use devm_platform_ioremap_resource()

Simplify the platform_get_resource() and devm_ioremap_resource()
calls with devm_platform_ioremap_resource().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Asmaa Mnebhi <asmaa@nvidia.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>