gpio: mlxbf3: use platform_get_irq_optional()

The gpio-mlxbf3 driver interfaces with two GPIO controllers,
device instance 0 and 1. There is a single IRQ resource shared
between the two controllers, and it is found in the ACPI table for
device instance 0. The driver should not use platform_get_irq(),
otherwise this error is logged when probing instance 1:
    mlxbf3_gpio MLNXBF33:01: error -ENXIO: IRQ index 0 not found

Cc: stable@vger.kernel.org
Fixes: cd33f216 ("gpio: mlxbf3: Add gpio driver support")
Signed-off-by: David Thompson <davthompson@nvidia.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/ce70b98a201ce82b9df9aa80ac7a5eeaa2268e52.1754928650.git.davthompson@nvidia.com


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>