xilinx.h: Added missing includes

Added some missing #includes for this file. Previously this file
relied on its clients to pre-include its dependencies.
Signed-off-by: NPeter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>
Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@gmail.com>

hw/xilinx.h

+#include "qemu-common.h"
+#include "net.h"
 
 /* OPB Interrupt Controller.  */
 qemu_irq *microblaze_pic_init_cpu(CPUState *env);