[mpp_buffer]: Signal codec thread on buffer create

When mpp codec thread go into idle status for lack of buffer new buffer
commit or create should wake up the codec thread to check again.

Change-Id: I843f7c790e1f8b8dcd67e209077f2475c8e265c8
Signed-off-by: Herman Chen <herman.chen@rock-chips.com>

mpp/base/mpp_buffer_impl.cpp

@@ -327,6 +327,11 @@ MPP_RET mpp_buffer_create(const char *tag, const char *caller,
         inc_buffer_ref_no_lock(p, caller);
         *buffer = p;
     }
+
+    if (group->listener) {
+        MppThread *thread = (MppThread *)group->listener;
+        thread->signal();
+    }
 RET:
     MPP_BUF_FUNCTION_LEAVE();
     return ret;