test_list_sort: fix up const mismatch

test_list_sort: fix up const mismatch

In the internal cmp function, a const pointer is cast out to a non-const
pointer by using container_of().  This is probably not what is intended
at all, so fix up the const marking to properly preserve what is really
happening (i.e. the const should flow through the container_of() call)

Cc: Jakub Kicinski <kuba@kernel.org>
Cc: David Gow <davidgow@google.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Kees Cook <kees@kernel.org>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: David Gow <davidgow@google.com>
Link: https://patch.msgid.link/2025121751-backtrack-manifesto-7c57@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>