selftests/powerpc: ptrace-pkey: Don't update expected UAMOR value

With commit 4a4a5e5d ("powerpc/pkeys: key allocation/deallocation
must not change pkey registers") we are not updating UAMOR on key
allocation. So don't update the expected uamor value in the test.

Fixes: 4a4a5e5d ("powerpc/pkeys: key allocation/deallocation must not change pkey registers")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-23-aneesh.kumar@linux.ibm.com