drivers: can: Add Renesas R-Car driver

This driver is for classic CAN, it makes use of CAN interface
in FIFO mode.

This driver support Standard ID as well as Extended ID.

Tested on H3ULCB, Ebisu platform, with external adapter and
in loopback mode.

Signed-off-by: Julien Massot <julien.massot@iot.bzh>