[PATCH] x86-64: Add option to compile for Core2

Add an option to compile for Intel's Core 2

The Kconfig help is a mouthful due to the inventiveness of Intel's
product naming department.

Mainly for the 64bit cache line sizes because gcc doesn't support
optimizing for core2 yet. However it will and then the kernel
should be ready by passing the right option

Also fix the old MPSC help text to confirm better to reality.

Signed-off-by: Andi Kleen <ak@suse.de>