gpio: vf610: Mask all GPIO interrupts

On SoC reset all GPIO interrupts are disable. However, if kexec is
used to boot into a new kernel, the SoC does not experience a
reset. Hence GPIO interrupts can be left enabled from the previous
kernel. It is then possible for the interrupt to fire before an
interrupt handler is registered, resulting in the kernel complaining
of an "unexpected IRQ trap", the interrupt is never cleared, and so
fires again, resulting in an interrupt storm.

Disable all GPIO interrupts before registering the GPIO IRQ chip.

Fixes: 7f2691a1

 ("gpio: vf610: add gpiolib/IRQ chip driver for Vybrid")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>