rtc: rv3029: use sysfs_emit() instead of sprintf()

Use sysfs_emit() instead of sprintf() in sysfs show callbacks
(rv3029_hwmon_show_temp and rv3029_hwmon_show_update_interval) to
conform to the recommended sysfs attribute formatting guidelines in
Documentation/filesystems/sysfs.rst.

Link: https://patch.msgid.link/20261029132339.925021-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>