selftests/powerpc: context_switch: Fix pthread errors

[Michael Ellerman]

On Tue, 2017-07-04 at 01:21:15 UTC, Cyril Bur wrote:
> Turns out pthreads returns an errno and doesn't set errno. This doesn't
> play well with perror().
> 
> Signed-off-by: Cyril Bur <cyrilbur at gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/89aca4753eb451a48f65a12b026403

cheers