The DHT22 sensor works using the 1-wire library. It seems that as of now there isn’t a library that supports the DHT sensors in the UPM repository. Take a look at Feature Request: 1-wire support · Issue #154 · intel-iot-devkit/mraa · GitHub .
However there are users who’ve successfully used DHT sensors with the Arduino IDE, take a look at DHT22 on edison arudino expansion board for the links of the libraries that have worked for other users. Additionally, take a look at Re: How can I test DHT11 sensor on edison+arduino board? . This thread has several links of other users using DHT sensors you might find useful.