[][Add trng device node for mt7981]

[Description]
Add trng device mode.

[Release-log]
N/A

Change-Id: Iba02f392920b2cb9edf5c2c63d8614391da79545
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5379897
diff --git a/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981.dtsi b/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981.dtsi
index f4d0b78..4e292da 100644
--- a/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981.dtsi
+++ b/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7981.dtsi
@@ -241,6 +241,10 @@
 		interrupts = <GIC_PPI 9 IRQ_TYPE_LEVEL_HIGH>;
 	};
 
+	trng: trng@1020f000 {
+		compatible = "mediatek,mt7981-rng";
+	};
+
 	uart0: serial@11002000 {
 		compatible = "mediatek,mt6577-uart";
 		reg = <0 0x11002000 0 0x400>;