rtc: sysfs: Use sysfs_emit() to instead of s*printf()

rtc: sysfs: Use sysfs_emit() to instead of s*printf()

Follow the advice of the Documentation/filesystems/sysfs.rst that show()
should only use sysfs_emit() or sysfs_emit_at() when formatting the value
to be returned to user space.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250702061534.2670729-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>