rtc: sysfs: fix hctosys_show kerneldoc

Fix undocumented function parameters:
drivers/rtc/sysfs.c:112: warning: Function parameter or member 'dev' not described in 'hctosys_show'
drivers/rtc/sysfs.c:112: warning: Function parameter or member 'attr' not described in 'hctosys_show'
drivers/rtc/sysfs.c:112: warning: Function parameter or member 'buf' not described in 'hctosys_show'

Link: https://lore.kernel.org/r/20191122102212.400158-2-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/sysfs.c

@@ -103,8 +103,11 @@ static DEVICE_ATTR_RW(max_user_freq);
 
 /**
  * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
+ * @dev: The device that the attribute belongs to.
+ * @attr: The attribute being read.
+ * @buf: The result buffer.
  *
- * Returns 1 if the system clock was set by this RTC at the last
+ * buf is "1" if the system clock was set by this RTC at the last
  * boot or resume event.
  */
 static ssize_t