x86/AMD: make use of CPUID leaf 0xb when available

x86/AMD: make use of CPUID leaf 0xb when available

Initially I did simply stumble across a backport of Linux commit
e0ceeae708 ("x86/CPU/hygon: Fix phys_proc_id calculation logic for
multi-die processors") to our kernels. There I got puzzled by the claim
that a similar change isn't needed on the AMD side. As per the web page
cited [1], there aren't supposed to be affected AMD processors, but
according to my reading there are: The EPYC 7000 series comes with 8,
16, 24, or 32 cores, which I imply to be 1, 2, 3, or 4 die processors.
And many of them have "1P/2P" in the "socket count" column. Therefore
our calculation, being based on CPUID.80000008.EBX[15:12], would be
similarly wrong on such 2-socket 1- or 2-die systems.

Checking Linux code I then found that they don't even rely on the
calculation we currently use anymore, at least not in the case when
leaf 0xb is available (which is the case on Fam17). Let's follow
Suravee's Linux commit 3986a0a805 ("x86/CPU/AMD: Derive CPU topology
from CPUID function 0xB when available") in this regard to address this.

To avoid logging duplicate information, make the function return bool.
Move its and detect_ht()'s declaration to a private header at the same
time.

[1] https://www.amd.com/en/products/specifications/processors

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>