can: rcar_canfd: Use of_get_available_child_by_name()

can: rcar_canfd: Use of_get_available_child_by_name()

Simplify rcar_canfd_probe() using of_get_available_child_by_name().

While at it, move of_node_put(child) inside the if block to avoid
additional check if of_child is NULL.

Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20250417054320.14100-4-biju.das.jz@bp.renesas.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>