i386: Use hv_build_cpuid_leaf() for HV_CPUID_NESTED_FEATURES

i386: Use hv_build_cpuid_leaf() for HV_CPUID_NESTED_FEATURES

Previously, HV_CPUID_NESTED_FEATURES.EAX CPUID leaf was handled differently
as it was only used to encode the supported eVMCS version range. In fact,
there are also feature (e.g. Enlightened MSR-Bitmap) bits there. In
preparation to adding these features, move HV_CPUID_NESTED_FEATURES leaf
handling to hv_build_cpuid_leaf() and drop now-unneeded 'hyperv_nested'.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220525115949.1294004-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>