IB/mlx5: Fix FW version diaplay in sysfs

Add a 4-digit padding to show FW version in proper format.

Fixes: 9603b61d ('mlx5: Move pci device handling from...')
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Noa Osherovich <noaos@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>