can: xilinx_can: clean up indentation issue

A statement is indented one level too deep, fix this.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NMichal Simek <michal.simek@xilinx.com>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>