ARM: dts: stih410: align HDMI CEC node names with dtschema

The bindings expect "cec" for HDMI CEC node.

Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20221204183353.140002-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>