Proposed #ifdef change to em

I have found that the FAST interrupt handling is  implicated
in the watchdog resets that I have seen.

What I plan to do is revert to the way 6.2 had things, meaning
that FAST interrupts will be available but defined off by default.

I wanted to know if anyone has an issue with this. And more
importantly, I have personally not seen this problem on 7, but
I could set up #ifdef's in that driver to be the same way.

What does everyone think?

Jack