Fix TCL issue when a hierarchy has multiple sub-hierarchies (#772)
Fix TCL issue when a hierarchy has multiple sub-hierarchies (#772)


cathalmccabe/PYNQ,cathalmccabe/PYNQ,schelleg/PYNQ,Xilinx/PYNQ,schelleg/PYNQ,Xilinx/PYNQ,cathalmccabe/PYNQ,schelleg/PYNQ,schelleg/PYNQ,schelleg/PYNQ,yunqu/PYNQ,yunqu/PYNQ,cathalmccabe/PYNQ,cathalmccabe/PYNQ,Xilinx/PYNQ,yunqu/PYNQ,yunqu/PYNQ,Xilinx/PYNQ,Xilinx/PYNQ,yunqu/PYNQ,cathalmccabe/PYNQ