Adjust vol dnd icon layout width

When only one volume row is visible, adjust the
width of the volume dnd icon FrameLayout so the
icon floats on the top right.  Icon was previously
inset by padding introcued by volume_dialog_rows minWidth
attribute.

Test: visual inspection (with 1+ streams)
Fixes: 78275139
Change-Id: I8f34ba21545823ac8431396696adb4e9347b40db