axi_dmac: Add xfer_req signal to the streamin AXI source interface

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
daq2/daq3/ad9625_fmc: Connect ADC DMA xfer_req signal

For proper operation the xfer_req signal needs to be connected from the ADC DMA to the DDR FIFO.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>