ARM: dts: stm32f429: put can2 in secondary mode

This is a preparation patch for the upcoming support to manage CAN
peripherals in single configuration.

The addition ensures backwards compatibility.
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://lore.kernel.org/all/20230427204540.3126234-3-dario.binacchi@amarulasolutions.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

arch/arm/boot/dts/stm32f429.dtsi

@@ -387,6 +387,7 @@ can2: can@40006800 {
 			interrupt-names = "tx", "rx0", "rx1", "sce";
 			resets = <&rcc STM32F4_APB1_RESET(CAN2)>;
 			clocks = <&rcc 0 STM32F4_APB1_CLOCK(CAN2)>;
+			st,can-secondary;
 			st,gcan = <&gcan>;
 			status = "disabled";
 		};