PWMin: Fix test cmd

src/drivers/pwm_input/pwm_input.cpp

@@ -599,6 +599,9 @@ static void pwmin_test(void)
 			       (unsigned)buf.period,
 			       (unsigned)buf.pulse_width,
 			       (unsigned)buf.error_count);
+		} else {
+			/* no data, retry in 2 ms */
+			::usleep(2000);
 		}
 	}