mm/page_alloc: fix doc for numa_zonelist_order

The default zonelist order selecter will select "node" order if any nodes
DMA zone comprises greater than 70% of its local memory instead of 60%,
according to default_zonelist_order::low_kmem_size > total * 70/100.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/sysctl/vm.txt

@@ -510,7 +510,7 @@ Specify "[Dd]efault" to request automatic configuration.  Autoconfiguration
 will select "node" order in following case.
 (1) if the DMA zone does not exist or
 (2) if the DMA zone comprises greater than 50% of the available memory or
-(3) if any node's DMA zone comprises greater than 60% of its local memory and
+(3) if any node's DMA zone comprises greater than 70% of its local memory and
     the amount of local memory is big enough.
 
 Otherwise, "zone" order will be selected. Default order is recommended unless