prod/optee/stm32mp2: restructure SCMI-clk description

Since commit 15e2236a ("mod/scmi_clock: Restructuring SCMI-clk module")
SCMI clock structures have changed. Adapt this product to the new
SCMI clock description structures.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>