RDMA/ipoib: Print a message if only child interface is UP

RDMA/ipoib: Print a message if only child interface is UP

When "enhanced IPoIB" is enabled for CX-5 devices it requires the parent
device to be UP, otherwise the child devices won't work.

Thus add a debug message to give admin a hint when only the child
interface is UP but parent interface is not.

Link: https://lore.kernel.org/r/20210408093215.24023-1-jinpu.wang@ionos.com
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>