Xen already collects CPUID.0x80000007.edx by default, meaning that we can
refer to per-cpu data directly. This also avoids the need IPI the onlining
CPU to identify whether Core Performance Boost is available.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>