bce(4) BCM5907 CTX write errors on 7.2 driver

[David Christensen]

> > Does the attached patch make a difference for you?
>
> This patch seems to do the trick, on at least one of the 
> R610's that we have.
> 
> Just did cold boot, 5 warm boots, cold boot, 5 warm boots and 
> have not had any issues.
>

Thanks for testing.  I want to pass the changes by a couple
other people before I go ahead with a commit.

Dave