x86: Use dmi check in apic_is_clustered() on 64-bit to mark the TSC unstable

We will have systems with 2 and more sockets 8cores/2thread,
but we treat them as multi chassis - while they could have
a stable TSC domain.

Use DMI check instead.

[ Impact: do not turn possibly stable TSCs off incorrectly ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Ravikiran Thirumalai <kiran@scalex86.org>
LKML-Reference: <49F5532A.5000802@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>