can: rcar_canfd: Improve error messages

Improve printed error messages:
  - Replace numerical error codes by mnemotechnic error codes, to
    improve the user experience in case of errors,
  - Drop parentheses around printed numbers, cfr.
    Documentation/process/coding-style.rst,
  - Drop printing of an error message in case of out-of-memory, as the
    core memory allocation code already takes care of this.

Suggested-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/4162cc46f72257ec191007675933985b6df394b9.1679414936.git.geert+renesas@glider.be


[mkl: use colon instead of comma]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>