hw/core/qdev-properties: Constify Property argument to PropertyInfo.print

hw/core/qdev-properties: Constify Property argument to PropertyInfo.print

This logically should have accompanied d36f165d952 which
allowed const Property to be registered.

There is exactly one instance of this method: print_pci_devfn.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Link: https://lore.kernel.org/r/20241218134251.4724-24-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>