[POWERPC] Change topology_init() to a subsys_initcall

Change the powerpc version of topology_init() from an __initcall to
a subsys_initcall to match all other architectures.
Signed-off-by: NKevin Corry <kevcorry@us.ibm.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/kernel/sysfs.c

@@ -499,4 +499,4 @@ static int __init topology_init(void)
 
 	return 0;
 }
-__initcall(topology_init);
+subsys_initcall(topology_init);