ARM: dts: stm32: Restore old usart1 clock bindings for stm32f7

As U-boot stm32f clock driver doesn't support new
bindings for auxiliary clocks (clocks = <&rcc 1 ....>),
restore old bindings for usart1 to get console output.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

arch/arm/dts/stm32f7-u-boot.dtsi

@@ -143,4 +143,5 @@
 
 &usart1 {
 	u-boot,dm-pre-reloc;
+	clocks = <&rcc 0 STM32F7_APB2_CLOCK(USART1)>;
 };