Leds are not part of soc, so nove them outside soc node.
This allows to fix the following warnings when compiling
dtb with W=1 option :

arch/arm/boot/dts/stih407-b2120.dtb: Warning (simple_bus_reg):
Node /soc/leds missing or empty reg/ranges property

arch/arm/boot/dts/stih410-b2120.dtb: Warning (simple_bus_reg):
Node /soc/leds missing or empty reg/ranges property

arch/arm/boot/dts/stih418-b2199.dtb: Warning (simple_bus_reg):
Node /soc/leds missing or empty reg/ranges property
Signed-off-by: NPatrice Chotard <patrice.chotard@st.com>