can: rcar_canfd: Fix data transmission failed on R-Car V3U

On R-Car V3U, this driver should use suitable register offset instead of
other SoCs' one. Otherwise, data transmission failed on R-Car V3U.

Fixes: 45721c40

 ("can: rcar_canfd: Add support for r8a779a0 SoC")
Link: https://lore.kernel.org/all/20220704074611.957191-1-yoshihiro.shimoda.uh@renesas.com
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Duy Nguyen <duy.nguyen.rh@renesas.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>