net/mlx5: select driver by class device argument

net/mlx5: select driver by class device argument

There might be a case that one Mellanox device can be probed by
multiple mlx5 drivers.

One case is that any mlx5 vDPA device can be probed by both net/mlx5
and vdpa/mlx5.

Add a new mlx5 common API to get the requested driver by devargs:
class=[net/vdpa].

Skip net/mlx5 PMD probing while the device is selected to be probed by
the vDPA driver.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>