[PATCH] fix mempolicy's check on a system with memory-less-node

bind_zonelist() can create zero-length zonelist if there is a
memory-less-node.  This patch checks the length of zonelist.  If length is
0, returns -EINVAL.

tested on ia64/NUMA with memory-less-node.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Andi Kleen <ak@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>