shutdown and also before we get going with the device initialization.
This may fix the hangs some people are seeing on warmboot. It appears
that some machines will reset the cardbus bridge on boot, while others
don't. So we turn off the card, and ack the interrupts (which likely
is a nop in the shutdown case since we're still fielding interrupts).
This should turn off the interrupts.
Since I don't have hardware that hangs on reboot, I'm committing this
without testing that aspect of the patch (it causes no harm on my
Dell).
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