RDMA/nldev: Check CAP_NET_RAW in user namespace for QP modify

RDMA/nldev: Check CAP_NET_RAW in user namespace for QP modify

Currently, the capability check is done in the default
init_user_ns user namespace. When a process runs in a
non default user namespace, such check fails. Due to this
when a process is running using Podman, it fails to modify
the QP.

Since the RDMA device is a resource within a network namespace,
use the network namespace associated with the RDMA device to
determine its owning user namespace.

Fixes: 0cadb4db79e1 ("RDMA/uverbs: Restrict usage of privileged QKEYs")
Signed-off-by: Parav Pandit <parav@nvidia.com>
Link: https://patch.msgid.link/099eb263622ccdd27014db7e02fec824a3307829.1750963874.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>