Technologic Systems provides an IP compatible with the SJA1000,
instantiated in an FPGA. Because of some bus widths issue, access to
registers is made through a "window" that works like this:

    base + 0x0: address to read/write
    base + 0x2: 8-bit register value

This commit adds a new compatible device, "technologic,sja1000", with
read and write functions using the window mechanism.
Signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>