ARM: dts: stm32mp1: add dsi host for stm32mp157c-dk2 board

The new class dsi host allows the management of the bridge DPI to DSI.
This bridge is embedded in the chipset mp1 (come from synopsys company).

Signed-off-by: Yannick Fertré <yannick.fertre@st.com>
diff --git a/arch/arm/dts/stm32mp157c-dk2-u-boot.dtsi b/arch/arm/dts/stm32mp157c-dk2-u-boot.dtsi
index 18ac1e3..cd9947f 100644
--- a/arch/arm/dts/stm32mp157c-dk2-u-boot.dtsi
+++ b/arch/arm/dts/stm32mp157c-dk2-u-boot.dtsi
@@ -5,6 +5,13 @@
 
 #include "stm32mp157a-dk1-u-boot.dtsi"
 
+/ {
+	dsi_host: dsi_host {
+		compatible = "synopsys,dw-mipi-dsi";
+		status = "okay";
+	};
+};
+
 &i2c1 {
 	hdmi-transmitter@39 {
 		reset-gpios = <&gpioa 10 GPIO_ACTIVE_LOW>;