mm/vmstat: move pgdemote_* out of CONFIG_NUMA_BALANCING

Demotion can work well without CONFIG_NUMA_BALANCING.  But the commit
23e9f013 ("mm/vmstat: move pgdemote_* to per-node stats") wrongly hid
it behind CONFIG_NUMA_BALANCING.

Fix it by moving them out of CONFIG_NUMA_BALANCING.

Link: https://lkml.kernel.org/r/20231229022651.3229174-1-lizhijian@fujitsu.com
Fixes: 23e9f013

 ("mm/vmstat: move pgdemote_* to per-node stats")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>