RDMA/nldev: Return context information

RDMA/nldev: Return context information

Extend the RDMA nldev return a context information, like ctx number and
process ID that created that context. This functionality is helpful to
find orphan contexts that are not closed for some reason.

Sample output:

$ rdma res show ctx
dev ibp8s0f0 ctxn 0 pid 980 comm ibv_rc_pingpong
dev ibp8s0f0 ctxn 1 pid 981 comm ibv_rc_pingpong
dev ibp8s0f0 ctxn 2 pid 992 comm ibv_rc_pingpong
dev ibp8s0f1 ctxn 0 pid 984 comm ibv_rc_pingpong
dev ibp8s0f1 ctxn 1 pid 987 comm ibv_rc_pingpong

$ rdma res show ctx dev ibp8s0f1
dev ibp8s0f1 ctxn 0 pid 984 comm ibv_rc_pingpong
dev ibp8s0f1 ctxn 1 pid 987 comm ibv_rc_pingpong

Link: https://lore.kernel.org/r/5c956acfeac4e9d532988575f3da7d64cb449374.1618753110.git.leonro@nvidia.com
Signed-off-by: Neta Ostrovsky <netao@nvidia.com>
Reviewed-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>