[rfa/ppc] De double compensate rs6000_frame_chain()

[Andrew Cagney]

> On Sep 26, 11:31am, Andrew Cagney wrote:
> 
> 
>> Ok to commit?
>> My GNU/Linux PPC shows no regressions.
> 
> 
> Yes!
> 
> Thanks for including the prefatory text in your email message describing
> the problem.

Committed,
Andrew