conf: simplify logic when checking for AUTOASSIGN PCI addresses

conf: simplify logic when checking for AUTOASSIGN PCI addresses

Old behavior: If the address was manually provided by config, copy
device AUTOASSIGN flag into the bus flag, and then later on in the
function *always* check for a match of the flags (which will always
match if the address came from config, since we just copied it).

New behavior: Don't mess with the bus flags - just directly check if
the AUTOASSIGN flag matches in bus and dev, but only make the check if
the address didn't come from config (i.e. it was auto-assigned by
libvirt).

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>