oprofile: Don't report Nehalem as core_2

This essentially reverts Linus' earlier 4b9f12a3779c548b68bc9af7d94030868ad3aa1b
commit. Nehalem is not core_2, so it shouldn't be reported as such.
However with the earlier arch perfmon patch it will fall back to
arch perfmon mode now, so there is no need to fake it as core_2.
The only drawback is that Linus will need to patch the arch perfmon
support into his oprofile binary now, but I think he can do that.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>