This commit extends the RDMA kernel verbs ABI to support the flush
operation defined in IBA A19.4.1. These changes are
backward compatible with the existing RDMA kernel verbs ABI.

It makes device/HCA support new FLUSH attributes/capabilities, and it
also makes memory region support new FLUSH access flags.

Users can use ibv_reg_mr(3) to register flush access flags. Only the
access flags also supported by device's capabilities can be registered
successfully.

Once registered successfully, it means the MR is flushable. Similarly,
A flushable MR should also have one or both of GLOBAL_VISIBILITY and
PERSISTENT attributes/capabilities like device/HCA.

Link: https://lore.kernel.org/r/20221206130201.30986-3-lizhijian@fujitsu.comReviewed-by: Zhu Yanjun <zyjzyj2000@gmail.com>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>