Workaround for "fatal firmware error" iwn(4) problem.

[Sean Bruno]

On Fri, 2014-05-16 at 20:06 +0200, Edward Tomasz Napierała wrote:
> I've started using FreeBSD laptop and iwn(4) failing at random moments
> like this...
> 
> May 16 17:11:54 brick kernel: iwn0: iwn_intr: fatal firmware error


so, interesting.  iwi(4) seems to do the same thing.  I'm not sure
what's up, but I've been trying to pin it down.

I suspect we've aggrivated something in the firmware recently.

sean