gpio: tegra: mask GPIO IRQs during IRQ shutdown

The driver currently leaves GPIO IRQs unmasked even when the GPIO IRQ
client has released the GPIO IRQ. This allows the HW to raise IRQs, and
SW to process them, after shutdown. Fix this by masking the IRQ when it's
shut down. This is usually taken care of by the irqchip core, but since
this driver has a custom irq_shutdown implementation, it must do this
explicitly itself.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Link: https://lore.kernel.org/r/20200427232605.11608-1-swarren@wwwdotorg.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>