Need to enable/disable all the counters instead of just counter 0.

This affects all cpus with family=6, including i386/core.  Usual symptom:
only counter 0 provides samples.  Other counters don't produce samples.
Signed-off-by: Arun Sharma <arun.sharma@google.com>
Cc: Philippe Elie <phil.el@wanadoo.fr>
Cc: John Levon <levon@movementarian.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>