oards/arm/efr32xg24_dk2601b: add support for sensors attached to I2C

Zephyr already have support for a couple of sensors on the board:
- Silicon Labs Si7210 hall effect sensor
- Silicon Labs Si7021 relative humidity & temperature sensor
- Vishay VEML6035 ambient light sensor

Add support for those in device tree.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>