[PATCH] count_vm_events() fix

Dopey bug.  Causes hopelessly-wrong numbers from vmstat(8) and several other
counters.

Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>