powerpc/papr_scm: Switch to numa_map_to_online_node()

Now that the core exports numa_map_to_online_node() switch to that
instead of the locally coded duplicate.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Oliver O'Halloran" <oohall@gmail.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Link: https://lore.kernel.org/r/157401276263.43284.12616818803654229788.stgit@dwillia2-desk3.amr.corp.intel.com


Reviewed-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/158188325830.894464.9454884523846454529.stgit@dwillia2-desk3.amr.corp.intel.com