tty: hvc_iucv: Drop unnecessary NULL check after container_of

tty: hvc_iucv: Drop unnecessary NULL check after container_of

The result of container_of() operations is never NULL unless the extracted
element is the first element of the embedded structure. This is not the
case here. The NULL check is therefore unnecessary and misleading.
Remove it.

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>
Link: https://lore.kernel.org/r/20210511012519.2359074-1-linux@roeck-us.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>