drivers: use PCI registration macro

drivers: use PCI registration macro

Simplify crypto and ethdev pci drivers init by using newly introduced
init macros and helpers.
Those drivers then don't need to register as "rte_driver"s anymore.

Exceptions:
- virtio and mlx* use RTE_INIT directly as they have custom initialization
  steps.
- VDEV devices are not modified - they continue to use PMD_REGISTER_DRIVER.

Update documentation for replacing an example referring to
PMD_REGISTER_DRIVER.

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