ACPI: TAD: Split acpi_tad_rtc_read_time()

Move the code converting a struct acpi_tad_rt into a struct rtc_time
from acpi_tad_rtc_read_time() into a new function, acpi_tad_rt_to_tm(),
to facilitate adding alarm support to the driver's RTC class device
interface going forward.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/9619488.CDJkKcVGEf@rafael.j.wysocki
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: rafaeljw

drivers/acpi/acpi_tad.c

@@ -617,6 +617,17 @@ static const struct attribute_group *acpi_tad_attr_groups[] = {
 #ifdef CONFIG_RTC_CLASS
 /* RTC class device interface */
 
+static void acpi_tad_rt_to_tm(struct acpi_tad_rt *rt, struct rtc_time *tm)
+{
+	tm->tm_year = rt->year - 1900;
+	tm->tm_mon = rt->month - 1;
+	tm->tm_mday = rt->day;
+	tm->tm_hour = rt->hour;
+	tm->tm_min = rt->minute;
+	tm->tm_sec = rt->second;
+	tm->tm_isdst = rt->daylight == ACPI_TAD_TIME_ISDST;
+}
+
 static int acpi_tad_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct acpi_tad_rt rt;
@@ -642,13 +653,7 @@ static int acpi_tad_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	if (ret)
 		return ret;
 
-	tm->tm_year = rt.year - 1900;
-	tm->tm_mon = rt.month - 1;
-	tm->tm_mday = rt.day;
-	tm->tm_hour = rt.hour;
-	tm->tm_min = rt.minute;
-	tm->tm_sec = rt.second;
-	tm->tm_isdst = rt.daylight == ACPI_TAD_TIME_ISDST;
+	acpi_tad_rt_to_tm(&rt, tm);
 
 	return 0;
 }