RDMA/nes: Fix incorrect SFP+ link status detection on driver init

During iw_nes initialization the link status for SFP+ PHY is always
detected as "up" regardless of real state (cable either connected or
disconnected).  Add SFP+ PHY specific link status detection to the
iw_nes initialization procedure.  Use link status recheck for
netdev_open to detect delayed state updates.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>