lib/sort: Add priv pointer to swap function

Adding support to have priv pointer in swap callback function.

Following the initial change on cmp callback functions [1]
and adding SWAP_WRAPPER macro to identify sort call of sort_r.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/bpf/20220316122419.933957-2-jolsa@kernel.org

[1] 4333fb96ca ("media: lib/sort.c: implement sort() variant taking context argument")

include/linux/types.h

@@ -226,6 +226,7 @@ struct callback_head {
 typedef void (*rcu_callback_t)(struct rcu_head *head);
 typedef void (*call_rcu_func_t)(struct rcu_head *head, rcu_callback_t func);
 
+typedef void (*swap_r_func_t)(void *a, void *b, int size, const void *priv);
 typedef void (*swap_func_t)(void *a, void *b, int size);
 
 typedef int (*cmp_r_func_t)(const void *a, const void *b, const void *priv);