RDMA/providers: Fix return value when QP type isn't supported

The proper return code is "-EOPNOTSUPP" when the requested QP type is
not supported by the provider.

Link: https://lore.kernel.org/r/20200130082049.463-1-kamalheib1@gmail.com
Signed-off-by: Kamal Heib <kamalheib1@gmail.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mthca/mthca_provider.c

@@ -561,7 +561,7 @@ static struct ib_qp *mthca_create_qp(struct ib_pd *pd,
 	}
 	default:
 		/* Don't support raw QPs */
-		return ERR_PTR(-ENOSYS);
+		return ERR_PTR(-EOPNOTSUPP);
 	}
 
 	if (err) {