usb: gadget: Drop unnecessary NULL checks after container_of

usb: gadget: Drop unnecessary NULL checks after container_of

The parameters passed to allow_link and drop_link functions are never NULL.
That means the result of container_of() on those parameters is also
never NULL, even though the reference into the structure points to the
first element of the structure. Remove the unnecessary NULL checks.

This change was made automatically with the following Coccinelle script.
A now obsolete 'out:' label was removed manually.

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

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

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Felipe Balbi <balbi@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210424145443.170413-1-linux@roeck-us.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>