Commit 8d93297 introduced a bug whereby non-inbuilt NICs are realized before
setting the default MAC address causing an assert. Switch NIC creation
over from pci_create_simple() to pci_create() which works exactly the
same except omitting the realize as originally intended.
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Artyom Tarasenko <atar4qemu@gmail.com>