Removed Intel 1G drivers (intel.lua).

Tagged with 'intel1g' so that we can revive them in the future when we
want to use them and have them in the lab. (Code safely in git history.)
Removed port.lua and selftest() functions that depend on it.

port.lua contained selftest functions operating directly on device
driver modules, but nowadays we should access drivers via App wrappers
and write tests as App networks.
intel10g.can_receive() changed to work under VFIO.

Checks the "descriptor done" flag of the RX-writeback buffer instead
of comparing rdt/rdh ring indices. (XXX Check performance cost.)
Require lib.hardware.bus in core.memory and core.app.

Temporary hack while we work out the best way to enable/init vfio.
intel_app: use vfio.

(Is this really needed?)
vhost_apps.selftest(): Run for 1 second instead of 10.