drivers: rtc: Add Maxim DS1337 RTC driver

This PR adds support for Maxim Integrated
DS1337 RTC chip.

Supported functionalities:
* Alarm interrupt (both alarms trigger INTA pin)
* Time setting/reading
* Both alarms setting/reading
* SQW frequency configuration

Tested on nRF52833-DK using rtc_api test set.

Signed-off-by: Marcin Lyda <elektromarcin@gmail.com>