x86/svm: Drop support for AMD's Lightweight Profiling

x86/svm: Drop support for AMD's Lightweight Profiling

Lightweight Profiling was introduced in Bulldozer (Fam15h), but was dropped
from Zen (Fam17h) processors.  Furthermore, LWP was dropped from Fam15/16 CPUs
when IBPB for Spectre v2 was introduced in microcode, owing to LWP not being
used in practice.

As a result, CPUs which are operating within specification (i.e. with up to
date microcode) no longer have this feature, and therefore are not using it.

Drop support from Xen.  The main motivation here is to remove unnecessary
complexity from CPUID handling, but it also tidies up the SVM code nicely.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Brian Woods <brian.woods@amd.com>