mlx4_core: Add extended port capabilities support

An Extended Port Info packet is sent to each hw port during HCA init.
If it returns without error, we assume the port supports extended port
capabilities.

Signed-off-by: Marcel Apfelbaum <marcela@dev.mellanox.co.il>
Reviewed-by: Jack Morgenstein <jackm@dev.mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>