Add helper function to interact with DMA driver using numpy (#286)
Add helper function to interact with DMA driver using numpy (#286)

* Add a function to the DMA class to get a numpy array from the buffer
* PEP 8 dma source file
* transfer function to use declared direction and length by default

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