dt-bindings: rng: mtk-rng: Add documentation for MT8516

This commit adds the device-tree documentation for the RNG IP on the
MediaTek MT8516 SoC.
Signed-off-by: Fabien Parent <fparent@baylibre.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/rng/mtk-rng.txt

@@ -6,6 +6,7 @@ Required properties:
 			"mediatek,mt7622-rng", 	"mediatek,mt7623-rng" : for MT7622
 			"mediatek,mt7629-rng",  "mediatek,mt7623-rng" : for MT7629
 			"mediatek,mt7623-rng" : for MT7623
+			"mediatek,mt8516-rng", "mediatek,mt7623-rng" : for MT8516
 - clocks	    : list of clock specifiers, corresponding to
 		      entries in clock-names property;
 - clock-names	    : Should contain "rng" entries;