net/mlx5: Added devlink info callback

The callback is invoked using 'devlink dev info <pci>' command and returns
the running and pending firmware version of the HCA and the name of the
kernel driver.

If there is a pending firmware version (a new version is burned but the
HCA still runs with the previous) it is returned as the stored
firmware version. Otherwise, the running version is returned for this
field.

Output example:
$ devlink dev info pci/0000:00:06.0
pci/0000:00:06.0:
  driver mlx5_core
  versions:
      fixed:
        fw.psid MT_0000000009
      running:
        fw.version 16.26.0100
      stored:
        fw.version 16.26.0100

Signed-off-by: Shay Agroskin <shayag@mellanox.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>