can: rcar_canfd: Fix R-Car V3U CAN mode selection

When adding support for R-Car V3U, the Global FD Configuration register
(CFDGFDCFG) and the Channel-specific CAN-FD Configuration Registers
(CFDCmFDCFG) were mixed up.  Use the correct register, and apply the
selected CAN mode to all available channels.

Annotate the corresponding register bits, to make it clear they do
not exist on older variants.

Fixes: 45721c40 ("can: rcar_canfd: Add support for r8a779a0 SoC")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/all/388ddf312917eb9f6cc460a481f68402a876f9b5.1674499048.git.geert+renesas@glider.be


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