dt-bindings: i2c: renesas, i2c: Document r8a7742 support

Document i2c controller for RZ/G1H (R8A7742) SoC, which is compatible
with R-Car Gen2 SoC family.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/i2c/renesas,i2c.txt

@@ -2,6 +2,7 @@ I2C for R-Car platforms
 
 Required properties:
 - compatible:
+	"renesas,i2c-r8a7742" if the device is a part of a R8A7742 SoC.
 	"renesas,i2c-r8a7743" if the device is a part of a R8A7743 SoC.
 	"renesas,i2c-r8a7744" if the device is a part of a R8A7744 SoC.
 	"renesas,i2c-r8a7745" if the device is a part of a R8A7745 SoC.