arm: dts: imx8mp: move firmware/optee node to common imx8mp-u-boot.dtsi

Move the firmware/optee node to the common imx8mp-u-boot.dtsi and
protect it with an ifdef CONFIG_OPTEE as it is a meaningless node
without the optee driver enabled.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/arch/arm/dts/imx8mp-u-boot.dtsi b/arch/arm/dts/imx8mp-u-boot.dtsi
index 200938a..694dea1 100644
--- a/arch/arm/dts/imx8mp-u-boot.dtsi
+++ b/arch/arm/dts/imx8mp-u-boot.dtsi
@@ -8,6 +8,15 @@
 	binman: binman {
 		multiple-images;
 	};
+
+#ifdef CONFIG_OPTEE
+	firmware {
+		optee {
+			compatible = "linaro,optee-tz";
+			method = "smc";
+		};
+	};
+#endif
 };
 
 &soc {