[RFC] cf rework to fix locking issues

[Holger Schurig]

> A while ago I reworked the CF flow to match that of the SDIO
> and USB drivers with respect to interrupt handling and
> callbacks into the core. This was in response to locking
> issues reported by Holger.  I got as far as this;
> unfortunately the card seems to stall during large transfers
> with this patch, but I'm not enough of a CF person to know how
> to debug it.

Ahh, so this trades an potential error against a real one?

What do you mean with "large"?   A flood ping ("ping -f"), or 
some 2 MB large file via SCP ?