target/i386: Check kvm_hyperv_expand_features() return value

In case more code is added after the kvm_hyperv_expand_features()
call, check its return value (since it can fail).

Fixes: 071ce4b0 ("i386: expand Hyper-V features during CPU feature expansion time")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230913093009.83520-2-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>