can: at91_can: fix section mismatch warning

...by adding the correct annotation "__devinit" to the driver's probe
function.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>