dt-bindings: dma: renesas,usb-dmac: Add binding for r8a774e1

Add binding for R8A774E1 SoC (RZ/G2H).

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Link: https://lore.kernel.org/r/1594919915-5225-13-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>