arm64: dts: renesas: r8a77990: Add cpg reset for DU

Add CPG reset properties to DU node of E3 (r8a77990) SoC.

According to Laurent Pinchart, R-Car Gen3 reset is handled at the group
level so specifying one reset entry per group is sufficient.
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm64/boot/dts/renesas/r8a77990.dtsi

@@ -1766,6 +1766,8 @@ du: display@feb00000 {
 			clocks = <&cpg CPG_MOD 724>,
 				 <&cpg CPG_MOD 723>;
 			clock-names = "du.0", "du.1";
+			resets = <&cpg 724>;
+			reset-names = "du.0";
 			vsps = <&vspd0 0 &vspd1 0>;
 			status = "disabled";