x86/oprofile: fix initialization of arch_perfmon for core_i7

Commit:

 e419294e

 x86/oprofile: moving arch_perfmon counter setup to op_x86_model_spec.init

introduced a bug in the initialization of core_i7 leading to the
incorrect model setup to &op_ppro_spec. This patch fixes this.

Signed-off-by: Robert Richter <robert.richter@amd.com>