amazon: validate IOPS only for io volumes

builder/amazon/common/block_device.go

@@ -181,12 +181,12 @@ func (b *BlockDevice) Prepare(ctx *interpolate.Context) error {
 			return fmt.Errorf("%s: the maximum ratio of provisioned IOPS to requested volume size "+
 				"(in GiB) is %v:1 for %s volumes", b.DeviceName, ratio, b.VolumeType)
 		}
-	}
 
 		if b.IOPS < minIops || b.IOPS > maxIops {
 			return fmt.Errorf("IOPS must be between %d and %d for device %s",
 				minIops, maxIops, b.DeviceName)
 		}
+	}
 
 	_, err := interpolate.RenderInterface(&b, ctx)
 	return err