mlx4: Sensing link type at device initialization

When bringing the port up, performing a SENSE_PORT command
To try and check to which physical link type (IB or Ethernet) the physical
port is connected.
In case there is no valid link partner, the port will come up as its
supported default.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>