dmaengine: usb-dmac: Add soctype for R-Car M3-W

This patch adds R-Car M3-W device tree bindings for usb-dmac driver.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>