x86/sev: Include XSS value in GHCB CPUID request

x86/sev: Include XSS value in GHCB CPUID request

When a guest issues a CPUID instruction for Fn0000000D_x01, the hypervisor may
be intercepting the CPUID instruction and need to access the guest XSS value.
For SEV-ES, the XSS value is encrypted and needs to be included in the GHCB to
be visible to the hypervisor.

Signed-off-by: John Allen <john.allen@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://patch.msgid.link/all/20250924200852.4452-3-john.allen@amd.com/