dt-bindings: mmc: renesas_sdhi: Add r8a77470 support

The RZ/G1C (a.k.a. R8A77470) comes with three SDHI interfaces,
SDHI0 and SDHI2 are compatible with R-Car Gen2 SDHIs, and
SDHI1 is compatible with R-Car Gen3 SDHIs, as it comes with an
internal DMAC, therefore SDHI1 is fully compatible with driver
renesas_sdhi_internal_dmac driver. As a result, the compatible
strings for the R8A77470 SDHI interfaces are a little bit special.
Document SDHI support for the RZ/G1C SoC.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/tmio_mmc.txt

@@ -19,6 +19,8 @@ Required properties:
 		"renesas,sdhi-r8a7744" - SDHI IP on R8A7744 SoC
 		"renesas,sdhi-r8a7745" - SDHI IP on R8A7745 SoC
 		"renesas,sdhi-r8a774a1" - SDHI IP on R8A774A1 SoC
+		"renesas,sdhi-r8a77470" - SDHI IP on R8A77470 SoC
+		"renesas,sdhi-mmc-r8a77470" - SDHI/MMC IP on R8A77470 SoC
 		"renesas,sdhi-r8a7778" - SDHI IP on R8A7778 SoC
 		"renesas,sdhi-r8a7779" - SDHI IP on R8A7779 SoC
 		"renesas,sdhi-r8a7790" - SDHI IP on R8A7790 SoC
@@ -35,8 +37,8 @@ Required properties:
 		"renesas,sdhi-r8a77995" - SDHI IP on R8A77995 SoC
 		"renesas,sdhi-shmobile" - a generic sh-mobile SDHI controller
 		"renesas,rcar-gen1-sdhi" - a generic R-Car Gen1 SDHI controller
-		"renesas,rcar-gen2-sdhi" - a generic R-Car Gen2 or RZ/G1
-					   SDHI controller
+		"renesas,rcar-gen2-sdhi" - a generic R-Car Gen2 and RZ/G1 SDHI
+					   (not SDHI/MMC) controller
 		"renesas,rcar-gen3-sdhi" - a generic R-Car Gen3 or RZ/G2
 					   SDHI controller