firmware: scmi: fix the multi channel support with CCF

When the CCF is activated, the dev->parent is not necessary
the reference to SCMI transport and the function devm_scmi_of_get_channel
failed for the registered SCMI clock, child for protocol@14,
the channel is null and the SCMI clock driver crash for any operations.

This patch changes the first parameter of the ops of_get_channel(),
aligned with other process_msg() to pass directly the good reference,
i.e. parent result of find_scmi_transport_device(dev)
which return the reference of the scmi transport device.

Fixes: 8e96801aa6a ("firmware: scmi: add multi-channel support")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/drivers/firmware/scmi/optee_agent.c b/drivers/firmware/scmi/optee_agent.c
index 2b2b8c1..db927fb 100644
--- a/drivers/firmware/scmi/optee_agent.c
+++ b/drivers/firmware/scmi/optee_agent.c
@@ -326,7 +326,7 @@
 static int scmi_optee_get_channel(struct udevice *dev,
 				  struct scmi_channel **channel)
 {
-	struct scmi_optee_channel *base_chan = dev_get_plat(dev->parent);
+	struct scmi_optee_channel *base_chan = dev_get_plat(dev);
 	struct scmi_optee_channel *chan;
 	u32 channel_id;
 	int ret;