usb: renesas_usbhs: Add compatible string for r8a7743/5

This patch adds support for r8a7743/5 SoCs. The Renesas RZ/G1[ME]
(R8A7743/5) usbhs is identical to the R-Car Gen2 family.

No driver change is needed due to the fallback compatible value
"renesas,rcar-gen2-usbhs".
Adding the SoC-specific compatible values here has two purposes:
  1. Document which SoCs have this hardware module,
  2. Allow checkpatch to validate compatible values.

Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Chris Paterson <chris.paterson2@renesas.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>