Update src/ipc/ipc4/readme.md

In the ipc4_bind sequence diagram, the steps call comp_set_sink() / comp_set_source(), but these functions don’t exist in the codebase (binding is done via buffer/graph connect + comp_bind/comp_buffer_connect flows).

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Liam Girdwood <lgirdwood@gmail.com>

Author: lgirdwood

src/ipc/ipc4/readme.md

@@ -92,8 +92,8 @@ sequenceDiagram
 
     IPC4Bind->>Buff: buffer_new() (Create Intermediate Storage)
 
-    IPC4Bind->>SrcMod: comp_set_sink(Buffer)
-    IPC4Bind->>SinkMod: comp_set_source(Buffer)
+    IPC4Bind->>SrcMod: Bind source pin to Buff (via comp_bind/comp_buffer_connect)
+    IPC4Bind->>SinkMod: Bind sink pin to Buff (via comp_bind/comp_buffer_connect)
 
     IPC4Bind-->>Host: Reply: Linked
     deactivate IPC4Bind