rtc: Add RTC range

Add a way for drivers to inform the core of the supported date/time range.
The core can then check whether the date/time or alarm is in the range
before calling ->set_time, ->set_mmss or ->set_alarm. It returns -ERANGE
when the time is out of range.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

include/linux/rtc.h

@@ -150,6 +150,9 @@ struct rtc_device {
 	bool nvram_old_abi;
 	struct bin_attribute *nvram;
 
+	time64_t range_min;
+	timeu64_t range_max;
+
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 	struct work_struct uie_task;
 	struct timer_list uie_timer;