qemu: command: Move PPC fdc check to domain validation

Apart from not littering the command line generator, the added benefit
is that new configs with a FDC will be rejected at define stage.

src/qemu/qemu_command.c

@@ -2258,14 +2258,6 @@ qemuBuildDiskDriveCommandLine(virCommandPtr cmd,
         qemuDomainSecretInfoPtr secinfo = diskPriv->secinfo;
         qemuDomainSecretInfoPtr encinfo = diskPriv->encinfo;
 
-        /* PowerPC pseries based VMs do not support floppy device */
-        if (disk->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY &&
-            qemuDomainIsPSeries(def)) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("PowerPC pseries machines do not support floppy device"));
-            return -1;
-        }
-
         if (disk->info.bootIndex) {
             bootindex = disk->info.bootIndex;
         } else {

src/qemu/qemu_process.c

@@ -4586,7 +4586,8 @@ qemuProcessStartValidateDisks(virDomainObjPtr vm,
     size_t i;
 
     for (i = 0; i < vm->def->ndisks; i++) {
-        virStorageSourcePtr src = vm->def->disks[i]->src;
+        virDomainDiskDefPtr disk = vm->def->disks[i];
+        virStorageSourcePtr src = disk->src;
 
         /* This is a best effort check as we can only check if the command
          * option exists, but we cannot determine whether the running QEMU
@@ -4599,6 +4600,14 @@ qemuProcessStartValidateDisks(virDomainObjPtr vm,
                              "QEMU binary"));
             return -1;
         }
+
+        /* PowerPC pseries based VMs do not support floppy device */
+        if (disk->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY &&
+            qemuDomainIsPSeries(vm->def)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("PowerPC pseries machines do not support floppy device"));
+            return -1;
+        }
     }
 
     return 0;