IPoIB: Remove a misleading debug print

Commit 732a2170 ("IB/ipoib: Bound the net device to the ipoib_neigh
structue") left a misleading debug print (n->dev would be a bond
device only if boding is used).  Clean it up.

Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>