[PATCHv1 8/8] Documentation: Add device tree bindings for Freescale VF610 sound.

[Xiubo Li-B47053]

> > +  -- Power supplies:
> > +     * Mic Bias
> > +
> > +  -- SGTL5000 pins:
> > +     * MIC_IN
> > +     * LINE_IN
> > +     * HP_OUT
> > +     * LINE_OUT
> 
> Things that are part of the CODEC should be part of the CODEC binding and
> this binding should reference that - this way the information doesn't
> have to be replicated by all boards using the CODEC and if new devices
> are supported by the CODEC driver then only that needs updating hopefully.
>

Yes, the "-- SGTL5000 pins:" should be in the CODEC binding.
But, actually the CODEC binding hasn't any reference about this.

So I added it here, but not very sure.