qemu: use qemuDomainMachineIsI440FX() in appropriate place

This patch makes qemuValideDevicePCISlotsChipsets() more consistent in
appearance by replacing several clauses of an if with the equivalent
call to qemuDomainMachineIsI440FX. The if was checking exactly the
same items, just in a slightly different order.

src/qemu/qemu_command.c

@@ -2110,11 +2110,7 @@ qemuValidateDevicePCISlotsChipsets(virDomainDefPtr def,
                                    virQEMUCapsPtr qemuCaps,
                                    virDomainPCIAddressSetPtr addrs)
 {
-    if ((STRPREFIX(def->os.machine, "pc-0.") ||
-        STRPREFIX(def->os.machine, "pc-1.") ||
-        STRPREFIX(def->os.machine, "pc-i440") ||
-        STREQ(def->os.machine, "pc") ||
-        STRPREFIX(def->os.machine, "rhel")) &&
+    if (qemuDomainMachineIsI440FX(def) &&
         qemuValidateDevicePCISlotsPIIX3(def, qemuCaps, addrs) < 0) {
         return -1;
     }