mm/mempolicy: use readable NUMA_NO_NODE macro instead of magic number

The caller of mpol_misplaced() already use NUMA_NO_NODE to check whether
current page node is misplaced, thus using NUMA_NO_NODE in
mpol_misplaced() instead of magic number is more readable.

Link: https://lkml.kernel.org/r/1b77c0ce21183fa86f4db250b115cf5e27396528.1627558356.git.baolin.wang@linux.alibaba.com


Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>