arm: Compile in Xilinx soft IP device models

Zynq can instantiate these IPs in the programmable logic. Add them to the ARM
target build so these devices can be added to the machine model.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Microblaze: Build Zynq device models

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>