It's helpful for automated testing if the test returns error codes back
to the calling program.

While we're here fix all the usages of %p to remove the double 0x, ie.
%p already includes 0x.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>