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: 8e96801a ("firmware: scmi: add multi-channel support")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>