hw/isa/piix4: Replace some magic IRQ constants

This is a follow-up on patch "malta: Move PCI interrupt handling from
gt64xxx_pci to piix4". gt64xxx_pci used magic constants, and probably
didn't want to use piix4-specific constants. Now that the interrupt
handing resides in piix4, its constants can be used.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220217101924.15347-7-shentey@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

hw/isa/piix4.c

@@ -61,10 +61,10 @@ static void piix4_set_irq(void *opaque, int irq_num, int level)
     /* now we change the pic irq level according to the piix irq mappings */
     /* XXX: optimize */
     pic_irq = s->dev.config[PIIX_PIRQCA + irq_num];
-    if (pic_irq < 16) {
+    if (pic_irq < ISA_NUM_IRQS) {
         /* The pic level is the logical OR of all the PCI irqs mapped to it. */
         pic_level = 0;
-        for (i = 0; i < 4; i++) {
+        for (i = 0; i < PIIX_NUM_PIRQS; i++) {
             if (pic_irq == s->dev.config[PIIX_PIRQCA + i]) {
                 pic_level |= pci_bus_get_irq_level(bus, i);
             }
@@ -315,7 +315,7 @@ DeviceState *piix4_create(PCIBus *pci_bus, ISABus **isa_bus, I2CBus **smbus)
                                NULL, 0, NULL);
     }
 
-    pci_bus_irqs(pci_bus, piix4_set_irq, pci_slot_get_pirq, s, 4);
+    pci_bus_irqs(pci_bus, piix4_set_irq, pci_slot_get_pirq, s, PIIX_NUM_PIRQS);
 
     return dev;
 }