f3probe/f3brew: add --reset-type=2

Reset type 2 does not reset, that is, it does nothing.
This parameter is only helpful to study the effects of cache on
the F3 algorithms.

libdevs.c

@@ -803,6 +803,12 @@ static int bdev_usb_reset(struct device *dev)
 	return 0;
 }
 
+static int bdev_none_reset(struct device *dev)
+{
+	UNUSED(dev);
+	return 0;
+}
+
 static void bdev_free(struct device *dev)
 {
 	struct block_device *bdev = dev_bdev(dev);
@@ -915,6 +921,9 @@ struct device *create_block_device(const char *filename, enum reset_type rt)
 	case RT_USB:
 		bdev->dev.reset = bdev_usb_reset;
 		break;
+	case RT_NONE:
+		bdev->dev.reset = bdev_none_reset;
+		break;
 	default:
 		assert(0);
 	}

libdevs.h

@@ -84,6 +84,7 @@ struct device *create_file_device(const char *filename,
 enum reset_type {
 	RT_MANUAL_USB = 0,
 	RT_USB,
+	RT_NONE,
 	RT_MAX
 };
 #define RT_DEFAULT	RT_MANUAL_USB

libutils.h

@@ -5,6 +5,8 @@
 #include <argp.h>	/* For struct argp_state.	*/
 #include <sys/time.h>	/* For struct timeval.		*/
 
+#define UNUSED(x)	((void)x)
+
 int ilog2(uint64_t x);
 
 /* Least power of 2 greater than or equal to x. */