gpio: mlxbf3: Support shutdown() function

During Linux graceful reboot, the GPIO interrupts are not disabled.
Since the drivers are not removed during graceful reboot,
the logic to call mlxbf3_gpio_irq_disable() is not triggered.
Interrupts that remain enabled can cause issues on subsequent boots.

For example, the mlxbf-gige driver contains PHY logic to bring up the link.
If the gpio-mlxbf3 driver loads first, the mlxbf-gige driver
will use a GPIO interrupt to bring up the link.
Otherwise, it will use polling.
The next time Linux boots and loads the drivers in this order, we encounter the issue:
- mlxbf-gige loads first and uses polling while the GPIO10
  interrupt is still enabled from the previous boot. So if
  the interrupt triggers, there is nothing to clear it.
- gpio-mlxbf3 loads.
- i2c-mlxbf loads. The interrupt doesn't trigger for I2C
  because it is shared with the GPIO interrupt line which
  was not cleared.

The solution is to add a shutdown function to the GPIO driver to clear and disable
all interrupts. Also clear the interrupt after disabling it in mlxbf3_gpio_irq_disable().

Fixes: 38a700ef ("gpio: mlxbf3: Add gpio driver support")
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240611171509.22151-1-asmaa@nvidia.com


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