RDMA/mlx5: Introduce GET_DATA_DIRECT_SYSFS_PATH ioctl

Introduce the 'GET_DATA_DIRECT_SYSFS_PATH' ioctl to return the sysfs
path of the affiliated 'data direct' device for a given device.

Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://patch.msgid.link/403745463e0ef52adbef681ff09aa6a29a756352.1722512548.git.leon@kernel.org


Signed-off-by: Leon Romanovsky <leon@kernel.org>