x86/debug: Dump family, model, stepping of the boot CPU

When acting on a user bug report, we find ourselves constantly
asking for /proc/cpuinfo in order to know the exact family,
model, stepping of the CPU in question.

Instead of having to ask this, add this to dmesg so that it is
visible and no ambiguities can ensue from looking at the
official name string of the CPU coming from CPUID and trying
to map it to f/m/s.

Output then looks like this:

[    0.146041] smpboot: CPU0: AMD FX(tm)-8100 Eight-Core Processor (fam: 15, model: 01, stepping: 02)

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Link: http://lkml.kernel.org/r/1347640666-13638-1-git-send-email-bp@amd64.org


[ tweaked it minimally to add commas. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>