mm: fixup /proc/vmstat output

Line up the vmstat_text with zone_stat_item

enum zone_stat_item {
	/* First 128 byte cacheline (assuming 64 bit words) */
	NR_FREE_PAGES,
	NR_INACTIVE,
	NR_ACTIVE,

We current have nr_active and nr_inactive reversed.

[ "OK with patch, though using initializers canbe handy to prevent such
   things in future:

	static const char * const vmstat_text[] = {
		[NR_FREE_PAGES] = "nr_free_pages",
		..."
							 - Alexey ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>