dt-bindings: fpga: add Stratix10 SoC FPGA manager binding

Add a Device Tree binding for the Intel Stratix10 SoC FPGA manager.
Signed-off-by: NAlan Tull <atull@kernel.org>
Signed-off-by: NRichard Gong <richard.gong@intel.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Acked-by: NMoritz Fischer <mdf@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/fpga/intel-stratix10-soc-fpga-mgr.txt

+Intel Stratix10 SoC FPGA Manager
+
+Required properties:
+The fpga_mgr node has the following mandatory property, must be located under
+firmware/svc node.
+
+- compatible : should contain "intel,stratix10-soc-fpga-mgr"
+
+Example:
+
+	firmware {
+		svc {
+			fpga_mgr: fpga-mgr {
+				compatible = "intel,stratix10-soc-fpga-mgr";
+			};
+		};
+	};