hw/acpi/piix4: No need to #include "hw/southbridge/piix.h"

hw/acpi/piix4 has its own header with its structure definition etc.

Ammends commit 2bfd0845f0 'hw/acpi/piix4: move PIIX4PMState into
separate piix4.h header'.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230121151941.24120-4-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/piix4.c

@@ -21,7 +21,6 @@
 
 #include "qemu/osdep.h"
 #include "hw/i386/pc.h"
-#include "hw/southbridge/piix.h"
 #include "hw/irq.h"
 #include "hw/isa/apm.h"
 #include "hw/i2c/pm_smbus.h"