RDMA/core: Support IB sub device with type "SMI"

RDMA/core: Support IB sub device with type "SMI"

This patch adds 2 APIs, as well as driver operations to support adding
and deleting an IB sub device, which provides part of functionalities
of it's parent.

A sub device has a type; for a sub device with type "SMI", it provides
the smi capability through umad for its parent, meaning uverb is not
supported.

A sub device cannot live without a parent. So when a parent is
released, all it's sub devices are released as well.

Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Link: https://lore.kernel.org/r/44253f7508b21eb2caefea3980c2bc072869116c.1718553901.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>