[PATCH] more-for_each_cpu-conversions fix

I screwed up this conversion - we should be iterating across online CPUs, not
possible ones.

Spotted by Joe Perches <joe@perches.com>

Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>