rpmsg: glink: Set tail pointer to 0 at end of FIFO

commit 4623e8bf upstream.

When wrapping around the FIFO, the remote expects the tail pointer to
be reset to 0 on the edge case where the tail equals the FIFO length.

Fixes: caf989c3 ("rpmsg: glink: Introduce glink smem based transport")
Cc: stable@vger.kernel.org
Signed-off-by: Chris Lew <clew@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/rpmsg/qcom_glink_smem.c

@@ -105,7 +105,7 @@ static void glink_smem_rx_advance(struct qcom_glink_pipe *np,
 	tail = le32_to_cpu(*pipe->tail);
 
 	tail += count;
-	if (tail > pipe->native.length)
+	if (tail >= pipe->native.length)
 		tail -= pipe->native.length;
 
 	*pipe->tail = cpu_to_le32(tail);