ethdev: convert to EAL hotplug

ethdev: convert to EAL hotplug

Remove bus logic from ethdev hotplug by using eal for this.

Current api is preserved:
- the last port that has been created is tracked to return it to the
  application when attaching,
- the internal device name is reused when detaching.

We can not get rid of ethdev hotplug yet since we still need some
mechanism to inform applications of port creation/removal to substitute
for ethdev hotplug api.

dev_type field in struct rte_eth_dev and rte_eth_dev_allocate are kept as
is, but this information is not needed anymore and is removed in the
following commit.

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