rtc: rv3029: update to support DM and sync with Linux 4.17

rtc: rv3029: update to support DM and sync with Linux 4.17

The "Flamingo" carrier-board for the RK3399-Q7 has a RV3029 populated
and the application will use the off-module RV3029 RTC including the
battery backed SRAM.

To support this use case, this commit includes the following changes:
 * updates the rv3029 driver to use DM
 * implements the read8/write8 operations

This syncs the implementation with the Linux code (based on 4.17),
porting the trickle-charger support from there (with improvements to
avoid unnecessary EEPROM updates) and adheres to the Linux DTS
binding.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Klaus Goger <klaus.goger@theobroma-systems.com>