tools: usb: testusb: update default vary for superspeed

Currently, default vary will not accomodate superspeed endpoints
causing unexpected babble errors in the IN direction. Let's update
default 'vary' parameter so that we can maintain a "short-less"
transfer as hinted at the comment.
Reported-by: NAmmy Yi <ammy.yi@intel.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>

tools/usb/testusb.c

@@ -387,6 +387,8 @@ int main (int argc, char **argv)
 	/* pick defaults that works with all speeds, without short packets.
 	 *
 	 * Best per-frame data rates:
+	 *     super speed,bulk      1024 * 16 * 8 = 131072
+	 *                 interrupt 1024 *  3 * 8 =  24576
 	 *     high speed, bulk       512 * 13 * 8 =  53248
 	 *                 interrupt 1024 *  3 * 8 =  24576
 	 *     full speed, bulk/intr   64 * 19     =   1216
@@ -395,7 +397,7 @@ int main (int argc, char **argv)
 	 */
 	param.iterations = 1000;
 	param.length = 1024;
-	param.vary = 512;
+	param.vary = 1024;
 	param.sglen = 32;
 
 	/* for easy use when hotplugging */
@@ -457,7 +459,7 @@ int main (int argc, char **argv)
 			"\t-c iterations		default 1000\n"
 			"\t-s transfer length	default 1024\n"
 			"\t-g sglen		default 32\n"
-			"\t-v vary			default 512\n",
+			"\t-v vary			default 1024\n",
 			argv[0]);
 		return 1;
 	}