drivers/bus: move driver assignment to end of probing

drivers/bus: move driver assignment to end of probing

The PCI mapping requires to know the PCI driver to use,
even before the probing is done. That's why the PCI driver is
referenced early inside the PCI device structure. See
commit 1d20a073fa5e ("bus/pci: reference driver structure before mapping")

However the rte_driver does not need to be referenced in rte_device
before the device probing is done.
By moving back this assignment at the end of the device probing,
it becomes possible to make clear the status of a rte_device.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Andrew Rybchenko <arybchenko@solarflare.com>
Tested-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Rosen Xu <rosen.xu@intel.com>