octeontx2-af: fix a use-after-free in rvu_nix_register_reporters

The rvu_dl will be freed in rvu_nix_health_reporters_destroy(rvu_dl)
after the create_workqueue fails, and after that free, the rvu_dl will
be translate back through the following call chain:

rvu_nix_health_reporters_destroy
  |-> rvu_nix_health_reporters_create
       |-> rvu_health_reporters_create
             |-> rvu_register_dl (label err_dl_health)

Finally. in the err_dl_health label, rvu_dl being freed again in
rvu_health_reporters_destroy(rvu) by rvu_nix_health_reporters_destroy.
In the second calls of rvu_nix_health_reporters_destroy, however,
it uses rvu_dl->rvu_nix_health_reporter, which is already freed at
the end of rvu_nix_health_reporters_destroy in the first call.

So this patch prevents the first destroy by instantly returning -ENONMEN
when create_workqueue fails. In addition, since the failure of
create_workqueue is the only entrence of label err, it has been
integrated into the error-handling path of create_workqueue.

Fixes: 5ed66306

 ("octeontx2-af: Add devlink health reporters for NIX")
Signed-off-by: Zhipeng Lu <alexious@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>