IB/mlx4: Fix memory leaks in ib_link_query_port()

If the call to mlx4_MAD_IFC() fails in ib_link_query_port() we will
currently do 'return err;' which will leak 'in_mad' and 'out_mad'.  We
should instead do 'goto out;' where we'll properly free the memory we
previously allocated.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>