Yealink W52P: update DECT base to firmware 25.73.0.25 (minor firmware update)

The Yealink release notes for this new firmware are here:
http://yealink.com/Upload/UCOne/2014.09.11/W52P_Release_Notes_of_Version73.pdf

As you can see in the release notes, the firmware has been updated for the base from 25.73.0.20 to 25.73.0.25, but the firmware of the handset is unchanged (26.73.0.10). I don't think we need a new name for the plugin for such a small change (there is just one new option in the config file: features.intercom.headset_prior.enable ; all the rest is unchanged)