dt-bindings: rcar-gen3-phy-usb2: Add r8a774b1 support

Document RZ/G2N (R8A774B1) SoC bindings.

Signed-off-by: Fabrizio Castro <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Yoshihiro Shimoda <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/phy/rcar-gen3-phy-usb2.txt

···
 	      SoC.
 	      "renesas,usb2-phy-r8a774a1" if the device is a part of an R8A774A1
 	      SoC.
+	      "renesas,usb2-phy-r8a774b1" if the device is a part of an R8A774B1
+	      SoC.
 	      "renesas,usb2-phy-r8a774c0" if the device is a part of an R8A774C0
 	      SoC.
 	      "renesas,usb2-phy-r8a7795" if the device is a part of an R8A7795