cxgb4i: Remove duplicate call to dst_neigh_lookup()

There is an extra call to dst_neigh_lookup() leftover in cxgb4i that can cause
an unreleased refcnt issue. Remove extraneous call.

Signed-off-by: Anish Bhatt <anish@chelsio.com>

Fixes : 759a0cc5 ('cxgb4i: Add ipv6 code to driver, call into libcxgbi ipv6 api')
Signed-off-by: David S. Miller <davem@davemloft.net>