phy: rcar-gen2: Add support for R-Car E2

This patch adds a compatible string to support for R-Car E2.

Signed-off-by: Yoshihiro Shimoda <[e-mail]>
Acked-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Simon Horman <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>

Documentation/devicetree/bindings/phy/rcar-gen2-phy.txt

···
 Required properties:
 - compatible: "renesas,usb-phy-r8a7790" if the device is a part of R8A7790 SoC.
 	      "renesas,usb-phy-r8a7791" if the device is a part of R8A7791 SoC.
+	      "renesas,usb-phy-r8a7794" if the device is a part of R8A7794 SoC.
 - reg: offset and length of the register block.
 - #address-cells: number of address cells for the USB channel subnodes, must
 		  be <1>.

drivers/phy/phy-rcar-gen2.c

···
 static const struct of_device_id rcar_gen2_phy_match_table[] = {
 	{ .compatible = "renesas,usb-phy-r8a7790" },
 	{ .compatible = "renesas,usb-phy-r8a7791" },
+	{ .compatible = "renesas,usb-phy-r8a7794" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, rcar_gen2_phy_match_table);