stm32mp1: Add remoteproc support for m4 coprocessor

Alignment with kernel patch proposal for binding:

[PATCH v4 0/8] stm32 m4 remoteproc on STM32MP157c
https://lkml.org/lkml/2019/5/14/159

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>

arch/arm/dts/stm32mp157a-dk1.dts

@@ -307,6 +307,12 @@
 	};
 };
 
+&m4_rproc {
+	mboxes = <&ipcc 0>, <&ipcc 1>, <&ipcc 2>;
+	mbox-names = "vq0", "vq1", "shutdown";
+	status = "okay";
+};
+
 &pwr {
 	pwr-regulators {
 		vdd-supply = <&vdd>;

arch/arm/dts/stm32mp157c-ed1.dts

@@ -217,6 +217,12 @@
 	status = "okay";
 };
 
+&m4_rproc {
+	mboxes = <&ipcc 0>, <&ipcc 1>, <&ipcc 2>;
+	mbox-names = "vq0", "vq1", "shutdown";
+	status = "okay";
+};
+
 &pwr {
 	pwr-regulators {
 		vdd-supply = <&vdd>;

arch/arm/dts/stm32mp157c.dtsi

@@ -1543,4 +1543,24 @@
 			status = "disabled";
 		};
 	};
+
+	mlahb {
+		compatible = "simple-bus";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		dma-ranges = <0x00000000 0x38000000 0x10000>,
+			     <0x10000000 0x10000000 0x60000>,
+			     <0x30000000 0x30000000 0x60000>;
+
+		m4_rproc: m4@10000000 {
+			compatible = "st,stm32mp1-m4";
+			reg = <0x10000000 0x40000>,
+			      <0x30000000 0x40000>,
+			      <0x38000000 0x10000>;
+			resets = <&rcc MCU_R>;
+			st,syscfg-holdboot = <&rcc 0x10C 0x1>;
+			st,syscfg-tz = <&rcc 0x000 0x1>;
+			status = "disabled";
+		};
+	};
 };