RDMA/rtrs: Rename rtrs_sess to rtrs_path

rtrs_sess is in fact a path. This makes it confusing and difficult to get
into the code. So let's rename the structure and related use cases of it.

Coccinelle was used to do the transformation for most of the occurrences
and remaining ones were handled manually.

Link: https://lore.kernel.org/r/20220105180708.7774-2-jinpu.wang@ionos.com


Signed-off-by: Vaishali Thakkar <vaishali.thakkar@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>