drivers: rtc: Add Texas Instruments BQ32002 RTC driver

This PR adds support for BQ32002 RTC chip.

Supported functionalities:

* Time setting/reading
* Alarm setting/reading
* Calibration setting/reading
* IRQ frequency configuration

Tested on nRF52833-DK board.

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