arch/sparc: increase CONFIG_NODES_SHIFT on SPARC64 to 5

SPARC M6-32 platform has (2^5) NUMA nodes, so need to bump up the
CONFIG_NODES_SHIFT to 5.

Orabug: 25577754

Signed-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Reviewed-by: Atish Patra <atish.patra@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>