eal: add hotplug operations for PCI and vdev

Hotplug invocations, which deals with devices, should come from the layer
that already handles them, i.e. EAL.

For both attach and detach operations, 'name' is used to select the bus
that will handle the request.

Signed-off-by: David Marchand <david.marchand@6wind.com>
Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>