dt-bindings: arm: socfpga: Add S10 System Manager binding

Add the device tree bindings for the Stratix10 System Manager.

Signed-off-by: Thor Thayer <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Reviewed-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/arm/altera/socfpga-system.txt

···
 		reg = <0xffd08000 0x1000>;
 		cpu1-start-addr = <0xffd080c4>;
 	};
+
+ARM64 - Stratix10
+Required properties:
+- compatible : "altr,sys-mgr-s10"
+- reg : Should contain 1 register range(address and length)
+        for system manager register.
+
+Example:
+	 sysmgr@ffd12000 {
+		compatible = "altr,sys-mgr-s10";
+		reg = <0xffd12000 0x228>;
+	};