Hide Dock speaker plays from sound pages

In order to ensure the setting only works on the analog docks, adding
the docking state checks.

Bug: 270492232
Test: manual test
1) Connect to digital dock
2) Check the sound page and the dock speaker plays shouldn't be
   displayed

Change-Id: I1dc1e0aac8b9067ec8f5f1defc721294caf2949e