net: at91_can: add braces {} to all arms of the statement

Braces {} should be used on all arms of this statement.

Link: https://lore.kernel.org/r/1624096589-13452-7-git-send-email-huangguangbin2@huawei.com


Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>