rtc: add new RTC_FEATURE_ALARM_WAKEUP_ONLY feature

Some RTCs have an IRQ pin that is not connected to a CPU interrupt but
rather directly to a PMIC or power supply. In that case, it is still useful
to be able to set alarms but we shouldn't expect interrupts.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220309162301.61679-22-alexandre.belloni@bootlin.com

include/uapi/linux/rtc.h

@@ -133,7 +133,8 @@ struct rtc_param {
 #define RTC_FEATURE_UPDATE_INTERRUPT	4
 #define RTC_FEATURE_CORRECTION		5
 #define RTC_FEATURE_BACKUP_SWITCH_MODE	6
-#define RTC_FEATURE_CNT			7
+#define RTC_FEATURE_ALARM_WAKEUP_ONLY	7
+#define RTC_FEATURE_CNT			8
 
 /* parameter list */
 #define RTC_PARAM_FEATURES		0