hw/i386/pc: Rename "bus" attribute to "pcibus"

The attribute is of type PCIBus; reflect that in the name. It will also make the
next change more intuitive.

Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Message-ID: <20240224135851.100361-3-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
9 files changed