VER-225: Improve RTC rv3028 driver to support BSM

[astrunin]

Added support BSM mode from DTS (0x01 for DSM, 0x03 for LSM)

RTC's EEPROM is updated only when the configuration changes, to improve it's lifetime (as in rv3028_set_trickle_charger)

[astrunin]

There is another way to set BSM mode that is already supported by the driver. But it only has API to userspace. There are RTC_PARAM_GET\RTC_PARAM_SET ioctls we can use to set RTC_PARAM_BACKUP_SWITCH_MODE parameter (there is a structure we need to pass to ioctl, it consists of parameter and value, value is, in our case RV3028_BACKUP_BSM_DSM - 0x1). For using this we don't need to make any changes in the driver, however we will need implimentation to be somewhere (not possible to do with a bash script)