tools/hvmloader: Fix non-deterministic cpuid()

tools/hvmloader: Fix non-deterministic cpuid()

hvmloader's cpuid() implementation deviates from Xen's in that the value
passed on ecx is unspecified. This means that when used on leaves that
implement subleaves it's unspecified which one you get; though it's more
than likely an invalid one.

Import Xen's implementation so there are no surprises.

Fixes: 318ac791f9f9 ("Add utilities needed for SMBIOS generation to hvmloader")
Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>