net: kcm: Replace fput with sockfd_put

The function sockfd_lookup uses fget on the value that is stored in
the file field of the returned structure, so fput should ultimately be
applied to this value.  This can be done directly, but it seems better
to use the specific macro sockfd_put, which does the same thing.

Perform a source code refactoring by using the following semantic patch.

    // <smpl>
    @@
    expression s;
    @@

       s = sockfd_lookup(...)
       ...
    + sockfd_put(s);
    - fput(s->file);
    // </smpl>

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>