x86/cpu/AMD: Apply the Erratum 688 fix when the BIOS doesn't

Some F14h machines have an erratum which, "under a highly specific
and detailed set of internal timing conditions" can lead to skipping
instructions and RIP corruption.

Add the fix for those machines when their BIOS doesn't apply it or
there simply isn't BIOS update for them.

Tested-by:  <mirh@protonmail.ch>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sherry Hurwitz <sherry.hurwitz@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yazen Ghannam <Yazen.Ghannam@amd.com>
Link: http://lkml.kernel.org/r/20171022104731.28249-1-bp@alien8.de
Link: https://bugzilla.kernel.org/show_bug.cgi?id=197285


[ Added pr_info() that we activated the workaround. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>