can: at91_can: at91_open(): forward request_irq()'s return value in case or an error

If request_irq() fails, forward the return value.

Link: https://lore.kernel.org/all/20231005-at91_can-rx_offload-v2-15-9987d53600e0@pengutronix.de


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