can: rcar_canfd: Add shared_can_regs variable to struct rcar_canfd_hw_info

R-Car Gen4 has shared regs for both CAN-FD and Classical CAN operations.
Add shared_can_regs variable to struct rcar_canfd_hw_info to handle this
difference.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20250417054320.14100-15-biju.das.jz@bp.renesas.com


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