xilinx.h: Dont qdev_create from ethernet_create()

Pulled the qdev_create functionality out of xilinx_axiethernet_create() and
pushed it up to the petalogix_ml605_mmu machine model. This makes the ethernet
create+init process consistent with the AXI DMA. Renamed function to
xilinx_axiethernet_init accordingly.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
xilinx.h: s/xilinx_axiethernetdma()/xilinx_axidma()

This function has nothing to do with ethernet. Its reusable for all DMA clients.
Dropped the "ethernet" in the name accordingly.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>