metag: Inhibit NUMA balancing.

The metag NUMA implementation follows the SH model, using different nodes for
memories with different latencies. As such, we ensure that automated balancing
between nodes is inhibited, by way of the new ARCH_WANT_VARIABLE_LOCALITY.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: James Hogan <james.hogan@imgtec.com>