Since the two functions are called together, let's consolidate them in
a new function rtrs_clt_destroy_sysfs_root.

Link: https://lore.kernel.org/r/20201217141915.56989-9-jinpu.wang@cloud.ionos.comSigned-off-by: NGuoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: NJack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>