[media] uvcvideo: freeing an error pointer

A recent cleanup introduced a potential dereference of -EFAULT when we
call kfree(map->menu_info).

Fixes: 4cc5bed1

 ("[media] uvcvideo: Use memdup_user() rather than duplicating its implementation")

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>