arm64: dt: poplar: add optee node

As Poplar supports running TF-A with OP-TEE as BL32
payload, add op-tee node in DT, which enables usage of
OP-TEE driver (which provides an interface for requesting services
from OP-TEE).

Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/arm/dts/hi3798cv200-poplar.dts

@@ -31,6 +31,13 @@
 		reg = <0x0 0x0 0x0 0x80000000>;
 	};
 
+	firmware {
+		optee {
+			compatible = "linaro,optee-tz";
+			method = "smc";
+		};
+	};
+
 	leds {
 		compatible = "gpio-leds";