Adjust volume offset as VC profile connection only

The previous volume bar is supported as LE audio profile connected. When
VCP standalone connection, we could use the volume seek bar to send the
volume offset command to the remote device for test

Bug: 234429084
Test: Connect PTS, and send the volume offset command
Change-Id: I4b4ba846e9d422c8ea737b7cd5215e5de684898c