sparc64: fix sparse warnings in int_64.c

Fix following warnings:
init_64.c:798:5: warning: symbol 'numa_cpu_lookup_table' was not declared. Should it be static?
init_64.c:799:11: warning: symbol 'numa_cpumask_lookup_table' was not declared. Should it be static?

The warnings were present with an allnoconfig
Fix so the variables are only declared if CONFIG_NEED_MULTIPLE_NODES is defined.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>