usb: r8a66597: Convert to USB DM

Convert the R8A66597 USB driver to DM and add support for DT probing.
Drop support for legacy non-DM and non-DT probing, since there are no
platform using that.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Chris Brandt <chris.brandt@renesas.com>