ARM: dts: stm32f429: Align Ethernet node with new bindings properties

This patch aligns clocks names and node reference according to new
stm32-dwmac glue binding. It also renames Ethernet pinctrl phandle
(indeed there is no need to add 0 as Ethernet instance as there is only
one IP in SOC).

Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>