ButtonStyle - fixed redundant anchors binding in panel.
ButtonStyle - fixed redundant anchors binding in panel.

Change-Id: I5c280e9571243f7d4f2ca517ba7320ebcd8ab615
Reviewed-by: J-P Nurmi <b84a892f57a298bb5dae653b4e188948a84d5549@digia.com>

mizukusak/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols,kobolabs/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols