coresight: Fix check in coresight_tmc_etr_buf_insert_barrier_packet

We request for "CORESIGHT_BARRIER_PKT_SIZE" length and we should
be happy when we get that size.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-tmc-etr.c

@@ -807,7 +807,7 @@ tmc_etr_buf_insert_barrier_packet(struct etr_buf *etr_buf, u64 offset)
 
 	len = tmc_etr_buf_get_data(etr_buf, offset,
 				   CORESIGHT_BARRIER_PKT_SIZE, &bufp);
-	if (WARN_ON(len <= CORESIGHT_BARRIER_PKT_SIZE))
+	if (WARN_ON(len < CORESIGHT_BARRIER_PKT_SIZE))
 		return -EINVAL;
 	coresight_insert_barrier_packet(bufp);
 	return offset + CORESIGHT_BARRIER_PKT_SIZE;