RDMA: Remove rdma_set_device_sysfs_group()

The driver's device group can be specified as part of the ops structure
like the device's port group. No need for the complicated API.

Link: https://lore.kernel.org/r/8964785a34fd3a29ff5b6693493f575b717e594d.1623427137.git.leonro@nvidia.com


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>