x86: Really print supported CPUs if PROCESSOR_SELECT=y

I'm sure it was a mere oversight that the CONFIG_ prefixes are
missing.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Dave Jones <davej@redhat.com>
LKML-Reference: <4D7118D30200007800034F79@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>