cpumask: convert node_to_cpumask_map[] to cpumask_var_t

Impact: fix (CONFIG_MAXSMP=y only) boot crash

c032ef60 "cpumask: convert
node_to_cpumask_map[] to cpumask_var_t" didn't get this one
conversion.  There was a compile warning, but I missed it.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Mike Travis <travis@sgi.com>
LKML-Reference: <200903132342.42813.rusty@rustcorp.com.au>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/mm/numa.c

@@ -61,7 +61,7 @@ const struct cpumask *cpumask_of_node(int node)
 		dump_stack();
 		return cpu_online_mask;
 	}
-	return &node_to_cpumask_map[node];
+	return node_to_cpumask_map[node];
 }
 EXPORT_SYMBOL(cpumask_of_node);
 #endif