mm: set correct numa_zonelist_order string when configured on the kernel command line

When numa_zonelist_order parameter is set to "node" or "zone" on the
command line it's still showing as "default" in sysctl.  That's because
early_param parsing function changes only user_zonelist_order variable.
Fix this by copying user-provided string to numa_zonelist_order if it was
successfully parsed.

Signed-off-by: Volodymyr G Lukiianyk <volodymyrgl@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>