vfs301: drop nr_enroll_stages override

Imaging drivers aren't allowed to change number of enroll stages anymore,
all that imaging driver does is providing image to the upper layer.
Upper layer decides if it needs more scans.

libfprint/drivers/vfs301.c

@@ -244,9 +244,6 @@ static int dev_open(struct fp_img_dev *dev, unsigned long driver_data)
 		return r;
 	}
 
-	/* Set enroll stage number */
-	dev->dev->nr_enroll_stages = 1;
-
 	/* Initialize private structure */
 	vdev = g_malloc0(sizeof(vfs301_dev_t));
 	dev->priv = vdev;