virpcimock: Create PCI devices under /sys/devices/pci*

virpcimock: Create PCI devices under /sys/devices/pci*

So far, we are creating devices directly under
/sys/bus/pci/devices/*. There is not much problem with it, but if
we really want to model kernel behaviour we need to create them
under /sys/devices/pciDDDD:BB and then only symlink them from the
old location.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>