RDMA/rtrs: server: Use already dereferenced rtrs_sess structure

The rtrs_sess structure has already been extracted above from the
rtrs_srv_sess structure. Use that to avoid redundant dereferencing.

Fixes: 9cb83748 ("RDMA/rtrs: server: main functionality")
Link: https://lore.kernel.org/r/20200522082833.1480551-1-haris.phnx@gmail.com


Signed-off-by: Md Haris Iqbal <haris.phnx@gmail.com>
Acked-by: Danil Kipnis <danil.kipnis@cloud.ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>