ARM: dts: sti: align LED node names with dtschema

The node names should be generic and DT schema expects certain pattern:

  stih407-b2120.dtb: leds: 'green', 'red' do not match any of the regexes: '(^led-[0-9a-f]$|led)', 'pinctrl-[0-9]+'

Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20221125144116.476877-1-krzysztof.kozlowski@linaro.org


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