selftests/powerpc: Fix subpage_prot test to return !0 on failure

[Michael Ellerman]

On Mon, 2016-02-05 at 04:54:29 UTC, Michael Ellerman wrote:
> It's helpful for automated testing if the test returns error codes back
> to the calling program.
> 
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>

Applied to powerpc next.

https://git.kernel.org/powerpc/c/3a19e500d8cdb39ef9ce128933

cheers