mailbox: qcom-ipcc: Fix IPCC mbox channel exhaustion

Fix IPCC (Inter-Processor Communication Controller) channel exhaustion by
setting the channel private data to NULL on mbox shutdown.

Err Logs:
remoteproc: MBA booted without debug policy, loading mpss
remoteproc: glink-edge: failed to acquire IPC channel
remoteproc: failed to probe subdevices for remoteproc: -16

Fixes: fa74a025 ("mailbox: Add support for Qualcomm IPCC")
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Cc: stable@vger.kernel.org
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/qcom-ipcc.c

@@ -155,6 +155,11 @@ static int qcom_ipcc_mbox_send_data(struct mbox_chan *chan, void *data)
 	return 0;
 }
 
+static void qcom_ipcc_mbox_shutdown(struct mbox_chan *chan)
+{
+	chan->con_priv = NULL;
+}
+
 static struct mbox_chan *qcom_ipcc_mbox_xlate(struct mbox_controller *mbox,
 					const struct of_phandle_args *ph)
 {
@@ -184,6 +189,7 @@ static struct mbox_chan *qcom_ipcc_mbox_xlate(struct mbox_controller *mbox,
 
 static const struct mbox_chan_ops ipcc_mbox_chan_ops = {
 	.send_data = qcom_ipcc_mbox_send_data,
+	.shutdown = qcom_ipcc_mbox_shutdown,
 };
 
 static int qcom_ipcc_setup_mbox(struct qcom_ipcc *ipcc)