x86/cpuid: Handle leaf 0x8000001c in guest_cpuid()

x86/cpuid: Handle leaf 0x8000001c in guest_cpuid()

Leaf 0x8000001c contains LWP information.  edx contains hardware supported
features (and is clamped against the maximum), while ecx and ebx contain
various properties of the implementation.  eax is entirely dynamic, depending
on xcr0 and MSR_LWP_CFG.

The call to guest_cpuid() in svm_update_lwp_cfg() can now be replaced by
reading the data straight out of the cpuid_policy block.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>