ARM: dts: stm32: support MIPI DSI on stm32f469-disco board

Unlike Linux, the DSI driver requires the LTDC clock to be properly
probed. Hence, the changes made to the DSI node.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>

arch/arm/dts/stm32f469-disco-u-boot.dtsi

@@ -92,7 +92,9 @@
 
 &dsi {
 	clocks = <&rcc 0 STM32F4_APB2_CLOCK(DSI)>,
+		 <&rcc 0 STM32F4_APB2_CLOCK(LTDC)>,
 		 <&clk_hse>;
+	clock-names = "pclk", "px_clk", "ref";
 };
 
 &gpioa {
@@ -140,6 +142,8 @@
 };
 
 &ltdc {
+	bootph-all;
+
 	clocks = <&rcc 0 STM32F4_APB2_CLOCK(LTDC)>;
 };