hw/isa/piix3: Merge hw/isa/piix4.c

Now that the PIIX3 and PIIX4 device models are sufficiently prepared, their
implementations can be merged into one file for further consolidation.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20231007123843.127151-20-shentey@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/isa/Kconfig b/hw/isa/Kconfig
index 17ddb25..040a18c 100644
--- a/hw/isa/Kconfig
+++ b/hw/isa/Kconfig
@@ -31,16 +31,7 @@
     select FDC_ISA
     select IDE_ISA
 
-config PIIX3
-    bool
-    select ACPI_PIIX4
-    select I8257
-    select IDE_PIIX
-    select ISA_BUS
-    select MC146818RTC
-    select USB_UHCI
-
-config PIIX4
+config PIIX
     bool
     # For historical reasons, SuperIO devices are created in the board
     # for PIIX4.