can: rcar_canfd: Add max_channels to struct rcar_canfd_hw_info

R-Car V3U supports a maximum of 8 channels whereas rest of the SoCs
support 2 channels.

Add max_channels variable to struct rcar_canfd_hw_info to handle this
difference.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/all/20221027082158.95895-3-biju.das.jz@bp.renesas.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>