rtc_time_to_tm: Fix signed / unsigned arithmetic

Hi all,

commit 945185a69daa457c4c5e46e47f4afad7dcea734f changed the some types in rtc_time_to_tm() to unsigned:

void rtc_time_to_tm(unsigned long time, struct rtc_time *tm) {
- register int days, month, year;
+ unsigned int days, month, year;

This doesn't work for all cases, because days is checked for < 0 later on:

if (days < 0) {
	year -= 1;
	days += 365 + LEAP_YEAR(year);
}

I think the correct fix would be to keep days signed and do an appropriate cast later on. See attached patch.

---

index 9f996ec..dd70bf7 100644
@@ -51,10 +51,11 @@ EXPORT_SYMBOL(rtc_year_days);
  */
 void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
 {
-	unsigned int days, month, year;
+	unsigned int month, year;
+	int days;
 
 	days = time / 86400;
-	time -= days * 86400;
+	time -= (unsigned int) days * 86400;
 
 	/* day of the week, 1970-01-01 was a Thursday */
 	tm->tm_wday = (days + 4) % 7;