IB: Move struct port_info from ipath to <rdma/ib_smi.h>

Move ipath's struct port_info into <rdma/ib_smi.h>, so that it can be
used by mthca to implement client reregister support.

Remove the __attribute__((packed)) because all the members of the struct
are naturally aligned anyway.

Signed-off-by: Leonid Arsh <leonida@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>