Fix the build for non-x86/ppc targets

Fix the build for non-x86/ppc targets

Since pci.c creates network devices, anything that links against pci.c
(everything) has to link against all network devices.  Since virtio-net
also requires virtio, we might as well link every target against all of
the virtio devices.

This suggests that the pci.c network device creation function needs some
refactoring.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6082 c046a42c-6fe2-441c-8c8c-71466251a162