can: at91/janz-ican3: replace snprintf() in show functions with sysfs_emit()

can: at91/janz-ican3: replace snprintf() in show functions with sysfs_emit()

The sysfs show() functions must not use snprintf() when formatting the
value to be returned to user space.

Fix the following coccicheck warning:
| drivers/net/can/at91_can.c:1185: WARNING: use scnprintf or sprintf.
| drivers/net/can/janz-ican3.c:1834: WARNING: use scnprintf or sprintf.
|
| Use sysfs_emit instead of scnprintf or sprintf makes more sense.

Link: https://lore.kernel.org/all/1634280624-4816-1-git-send-email-wangqing@vivo.com
Signed-off-by: Qing Wang <wangqing@vivo.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>