IB: Add node_guid to struct ib_device

Add a node_guid field to struct ib_device.  It is the responsibility
of the low-level driver to initialize this field before registering a
device with the midlayer.  Convert everyone to looking at this field
instead of calling ib_query_device() when all they want is the node
GUID, and remove the node_guid field from struct ib_device_attr.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>