[PATCH] x86_64: Allow oprofile for model P4 models

Add it for P4 model 6 - reported to work and have a similar PMU to
earlier P4s.

Add an p4force=1 module override parameter for future use.

We had a discussion about that earlier - it's a trade off between the
PMU staying compatible or not.  I think the force parameter is a
reasonable compromise.

Cc: oprofile-list@lists.sf.net
Cc: Asit Mallick <asit.k.mallick@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>