powerpc/lib: Fix randconfig build failure in sstep.c

[Michael Ellerman]

On Fri, 2016-11-18 at 00:57:18 UTC, Michael Ellerman wrote:
> Under some configs we need to explicitly include cpu_has_feature.h,
> otherwise we fail with:
> 
>   arch/powerpc/lib/sstep.c:1992:7: error: implicit declaration of function 'cpu_has_feature'
> 
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Applied to powerpc next.

https://git.kernel.org/powerpc/c/5e9d0e3d9ea6f771fa9fc9dbb65b54

cheers