ARM: dts: stm32mp1: add dsi host for stm32mp157c-ev1 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-ev1-u-boot.dtsi b/arch/arm/dts/stm32mp157c-ev1-u-boot.dtsi
index ec60486..af5945d 100644
--- a/arch/arm/dts/stm32mp157c-ev1-u-boot.dtsi
+++ b/arch/arm/dts/stm32mp157c-ev1-u-boot.dtsi
@@ -14,6 +14,11 @@
 		spi0 = &qspi;
 		usb0 = &usbotg_hs;
 	};
+
+	dsi_host: dsi_host {
+		compatible = "synopsys,dw-mipi-dsi";
+		status = "okay";
+	};
 };
 
 &flash0 {