usb: renesas_usbhs: Add support for RZ/A2

The RZ/A2 is similar to the R-Car Gen3 with some small differences.

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>