arm64: zynqmp: Add support for zynqmp nvmem firmware driver

Add support for zynqmp nvmem firmware driver.
Signed-off-by: Nava kishore Manne <nava.manne@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
[m.tretter@pengutronix.de: move to subnode of firmware]
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>

arch/arm64/boot/dts/xilinx/zynqmp.dtsi

@@ -120,6 +120,16 @@ zynqmp_firmware: zynqmp-firmware {
 			compatible = "xlnx,zynqmp-firmware";
 			method = "smc";
 
+			nvmem_firmware {
+				compatible = "xlnx,zynqmp-nvmem-fw";
+				#address-cells = <1>;
+				#size-cells = <1>;
+
+				soc_revision: soc_revision@0 {
+					reg = <0x0 0x4>;
+				};
+			};
+
 			zynqmp_pcap: pcap {
 				compatible = "xlnx,zynqmp-pcap-fpga";
 			};