The previous setting of 13 caused build errors:
In file included from include/linux/topology.h:32:0,
from include/linux/sched.h:78,
from arch/powerpc/kernel/asm-offsets.c:17:
include/linux/mmzone.h:961:2: error: #error Allocator MAX_ORDER exceeds SECTION_SIZE
make[1]: *** [arch/powerpc/kernel/asm-offsets.s] Error 1