Slight interface change on the watchdog fido

[Nick Hibma]

> It would be nice to not lose the comments.  Might also be nice to reduce the
> diff (so it doesn't have to reindent everything) by just adding a simple test
> after masking off WD_INTERVAL like so:
>
> 	if (cmd == 0 || cmd >= 64) {
> 		ipmi_set_watchdog(sc, 0);
> 		return;
> 	}

The code path pretty much requires the

 	if (cmd > 0 && valid(cmd) {
 		wd(set);
 		*error = 0;
 	} else if (wd(active)) {
 		wd(disable);
 	}

due to the way *error was defined.

I've added back the comments that were more than trivial.

Nick