Increase the asymetric memory depth on the DAC side. Increase the
data width of the grey coder and decoder.
The controller fills up the CDC memory with three AXI burst, to prevent
underflow on the wrap arounds.
Update the readback logic of the FIFO. The controller uses a
relative address counter, which counts the DMA beats. The readback
logic uses the last value of that counter to define the wrapping
address. The aditional data from the last AXI burst, if there is any,
will be dropped.