net/sched: taprio: Drop unnecessary NULL check after container_of

The rcu_head pointer passed to taprio_free_sched_cb is never NULL.
That means that the result of container_of() operations on it is also
never NULL, even though rcu_head is the first element of the structure
embedding it. On top of that, it is misleading to perform a NULL check
on the result of container_of() because the position of the contained
element could change, which would make the check invalid. Remove the
unnecessary NULL check.

This change was made automatically with the following Coccinelle script.

@@
type t;
identifier v;
statement s;
@@

<+...
(
  t v = container_of(...);
|
  v = container_of(...);
)
  ...
  when != v
- if (\( !v \| v == NULL \) ) s
...+>

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>