s390/compat: correct restore of high gprs on signal return

[Kamal Mostafa]

On Sun, 2016-02-28 at 10:14 -0700, Tim Gardner wrote:
> commit 342300cc9cd3428bc6bfe5809bfcc1b9a0f06702 looks like good
> material 
> for stable 3.8+.
> -- 
> Tim Gardner tim.gardner at canonical.com

Its actually only suitable for 3.19+ (the cc: stable tag in the patch
is wrong).  I'll ensure that it gets queued up for 3.19 and 4.2.

Thanks Tim!

 -Kamal