i2c: sh_mobile: document support for r8a7796 (R-Car M3-W)

Explicitly list per-SoC binding for r8a7796. No driver change
is required as the initialisation sequence is currently the same
as for the R-Car Gen3 fallback binding.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit 45345e9)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

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

@@ -10,6 +10,7 @@ Required properties:
 			- "renesas,iic-r8a7793" (R-Car M2-N)
 			- "renesas,iic-r8a7794" (R-Car E2)
 			- "renesas,iic-r8a7795" (R-Car H3)
+			- "renesas,iic-r8a7796" (R-Car M3-W)
 			- "renesas,iic-sh73a0" (SH-Mobile AG5)
 			- "renesas,rcar-gen2-iic" (generic R-Car Gen2 compatible device)
 			- "renesas,rcar-gen3-iic" (generic R-Car Gen3 compatible device)