x86, intel: Use c->microcode for Atom errata check

Now that the cpu update level is available the Atom PSE errata
check can use it directly without reading the MSR again.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1318466795-7393-2-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>