plasmoid: Make it possible to connect to a device using a touchscreen

Summary:
At the moment the button was only shown on hover. Now it will also be
shown when the details are expanded, which happens on tap.

Test Plan: Connected to my headphones.

Reviewers: #plasma, bshah, ngraham

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D19962