RDMA/rxe: Extend rxe packet format to support flush

Extend rxe opcode tables, headers, helper and constants to support
flush operations.

Refer to the IBA A19.4.1 for more FETH definition details

Link: https://lore.kernel.org/r/20221206130201.30986-6-lizhijian@fujitsu.com


Reviewed-by: Zhu Yanjun <zyjzyj2000@gmail.com>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>