RDMA/IPoIB: Fix error code return in ipoib_mcast_join

Return the error code in case of ib_sa_join_multicast fail.

Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Link: https://lore.kernel.org/r/20231121130316.126364-2-jinpu.wang@ionos.com


Signed-off-by: Leon Romanovsky <leon@kernel.org>