axi_dmac: Sync AXI signal names to Vivado

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
axi_dmac: Add support for DMA bus widths other than 64 bit

There were a few place in the core where it assumed a 64-bit wide bus. Make this
configurable using parameters. The patch also adds support for having different
DMA bus widths on the source and destination side.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
axi_ad9122: Add support for 128-bit wide DMA

Using 128-bit wide DMA makes it possible to send one sample each clock cycle.

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