drivers: sensor: add vishay veml6031 ambient light sensor

- add driver for Vishay VEML6031 High Accuracy Ambient Light Sensor.
- add new compatible "vishay,veml6031".
- read and write consecutive 8 bit registers as bulk operation.
- add driver to build all test of sensors.
- support fetch and get.
- triggered mode and interrupt is not yet supported.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>