fpga zynq: Add missing \n to messages

Function dev_err doesn't add a newline at the end of the string. This will
lead to a hard to read kernel log.

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