selftests/bpf: update bpf_wq_set_callback macro

Subsequent patch introduces bpf_wq_set_callback kfunc with an
implicit bpf_prog_aux argument.

To ensure backward compatibility add a weak declaration and make
bpf_wq_set_callback macro to check for the new kfunc first.

Signed-off-by: Ihor Solodrai <[email protected]>

Author: theihor

tools/testing/selftests/bpf/bpf_experimental.h

@@ -583,8 +583,13 @@ extern int bpf_wq_start(struct bpf_wq *wq, unsigned int flags) __weak __ksym;
 extern int bpf_wq_set_callback_impl(struct bpf_wq *wq,
 		int (callback_fn)(void *map, int *key, void *value),
 		unsigned int flags__k, void *aux__ign) __ksym;
+extern int bpf_wq_set_callback(struct bpf_wq *wq,
+		int (callback_fn)(void *map, int *key, void *value),
+		unsigned int flags) __weak __ksym;
 #define bpf_wq_set_callback(timer, cb, flags) \
-	bpf_wq_set_callback_impl(timer, cb, flags, NULL)
+	(bpf_wq_set_callback ? \
+		bpf_wq_set_callback(timer, cb, flags) : \
+		bpf_wq_set_callback_impl(timer, cb, flags, NULL))
 
 struct bpf_iter_kmem_cache;
 extern int bpf_iter_kmem_cache_new(struct bpf_iter_kmem_cache *it) __weak __ksym;