[PATCH] x86_64: Don't assume future AMD CPUs have K8 compatible performance counters

The NMI watchdog code did this incorrectly

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>