KVM: SVM: Assert that Hyper-V's HV_SVM_EXITCODE_ENL == SVM_EXIT_SW

KVM: SVM: Assert that Hyper-V's HV_SVM_EXITCODE_ENL == SVM_EXIT_SW

Add a build-time assertiont that Hyper-V's "enlightened" exit code is that,
same as the AMD-defined "Reserved for Host" exit code, mostly to help
readers connect the dots and understand why synthesizing a software-defined
exit code is safe/ok.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://patch.msgid.link/20251230211347.4099600-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>