module_adapter: add forward declarations for comp_dev/timestamp_data

Commit 9cc6454 ("module_adapter: Extend the module interface for
endpoint devices") added use of struct comp_dev and struct
timestamp_data to module_interface.h without required include header
and/or forward declarations. This leads to compiler warnings. Address
the issue by adding forward declarations for these structs as
implementation details are not needed in this header.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>

src/include/sof/audio/module_adapter/module/module_interface.h

@@ -67,6 +67,9 @@ struct output_stream_buffer {
 	uint32_t size; /* size of data in the buffer */
 };
 
+struct comp_dev;
+struct timestamp_data;
+
 /**
  * \struct module_endpoint_ops
  * \brief Ops relevant only for the endpoint devices such as the host copier or DAI copier.