fpga zynq: Remove priv->dev

socfpga uses mgr->dev for debug prints, there should be consistency
here, so standardize on that. The only other use was for dma
which can be replaced with mgr->dev.parent.

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Acked-by: Alan Tull <atull@opensource.altera.com>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>