can: rcar_canfd: Improve printing of global operational state

Replace the printing of internal numerical values by the printing of
strings reflecting their meaning, to make the message self-explanatory.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa@kernel.org>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/14c8c5ce026e9fec128404706d1c73c8ffa11ced.1716973640.git.geert+renesas@glider.be


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