x86/cpu/topology: Provide detect_extended_topology_early()

x86/cpu/topology: Provide detect_extended_topology_early()

To support force disabling of SMT it's required to know the number of
thread siblings early. detect_extended_topology() cannot be called before
the APIC driver is selected, so split out the part which initializes
smp_num_siblings.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Orabug: 28220674
CVE: CVE-2018-3620

(cherry picked from commit 95f3d39ccf7aaea79d1ffdac1c887c2e100ec1b6)

Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Conflicts:
	arch/x86/kernel/cpu/cpu.h
	arch/x86/kernel/cpu/topology.c
Contextual