Specifies the RTC Alarm Masks. This parameter can be a value of RTC_LL_EC_ALMA_MASK for ALARM A or RTC_LL_EC_ALMB_MASK for ALARM B. This feature can be modified afterwards using unitary function LL_RTC_ALMA_SetMask() for ALARM A or LL_RTC_ALMB_SetMask() for ALARM B.