i2c: rcar: document R8A77980 bindings

R-Car V3H (R8A77980) SoC also has the R-Car gen3 compatible I2C controller,
so document the SoC  specific bindings.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-rcar.txt

@@ -15,6 +15,7 @@ Required properties:
 	"renesas,i2c-r8a7796" if the device is a part of a R8A7796 SoC.
 	"renesas,i2c-r8a77965" if the device is a part of a R8A77965 SoC.
 	"renesas,i2c-r8a77970" if the device is a part of a R8A77970 SoC.
+	"renesas,i2c-r8a77980" if the device is a part of a R8A77980 SoC.
 	"renesas,i2c-r8a77995" if the device is a part of a R8A77995 SoC.
 	"renesas,rcar-gen1-i2c" for a generic R-Car Gen1 compatible device.
 	"renesas,rcar-gen2-i2c" for a generic R-Car Gen2 or RZ/G1 compatible