mm/mempolicy: remove redundant check in get_nodes

mm/mempolicy: remove redundant check in get_nodes

We have already checked whether maxnode is a page worth of bits, by:
    maxnode > PAGE_SIZE*BITS_PER_BYTE

So no need to check it once more.

Link: http://lkml.kernel.org/r/1510882624-44342-2-git-send-email-xieyisheng1@huawei.com
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Chris Salls <salls@cs.ucsb.edu>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Tan Xiaojun <tanxiaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>