arm64: dts: renesas: r8a77995: Add CAN external clock support

Adds external CAN clock node for r8a77995. This clock can be used as
fCAN clock of CAN and CAN FD controller.

Based on a patch for r8a7796 by Chris Paterson.
Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a77995.dtsi

@@ -51,6 +51,13 @@ extal_clk: extal {
 		clock-frequency = <0>;
 	};
 
+	/* External CAN clock - to be overridden by boards that provide it */
+	can_clk: can {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <0>;
+	};
+
 	scif_clk: scif {
 		compatible = "fixed-clock";
 		#clock-cells = <0>;