rtc: rv3032: Add a driver for Microcrystal RV-3032

New driver for the Microcrystal RV-3032, including support for:
 - Date/time
 - Alarms
 - Low voltage detection
 - Trickle charge
 - Trimming
 - Clkout
 - RAM
 - EEPROM
 - Temperature sensor

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201013144110.1942218-3-alexandre.belloni@bootlin.com