rtc: pcf2127: fix alarm handling

rtc: pcf2127: fix alarm handling

Fix multiple issues when handling alarms:
 - Use threaded interrupt to avoid scheduling when atomic
 - Stop matching on week day as it may not be set correctly
 - Avoid parsing the DT interrupt and use what is provided by the i2c or
   spi subsystem
 - Avoid returning IRQ_NONE in case of error in the interrupt handler
 - Never write WDTF as specified in the datasheet
 - Set uie_unsupported, as for the pcf85063, setting alarms every seconds
   is not working correctly and confuses the RTC.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200812085114.474903-1-alexandre.belloni@bootlin.com