x86, cpu: Fix detection of Celeron Covington stepping A1 and B0

Steppings A1 and B0 of Celeron Covington are currently misdetected as
Pentium II (Dixon). Fix it by removing the stepping check.

[ hpa: this fixes this specific bug... the CPUID documentation
  specifies that the L2 cache size can disambiguate additional CPUs;
  this patch does not fix that. ]

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Link: http://lkml.kernel.org/r/201105162138.15416.linux@rainbow-software.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>