audio: (cosmetic) address comments to an earlier PR

Address two cosmetic comments to
#10702

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

Author: lyakh

src/audio/module_adapter/module_adapter.c

@@ -69,7 +69,7 @@ static struct vregion *module_adapter_dp_heap_new(const struct comp_ipc_config *
 	 * A 1-to-1 replacement of the original heap implementation would be to
 	 * have "lifetime size" equal to 0. But (1) this is invalid for
 	 * vregion_create() and (2) we gradually move objects, that are simple
-	 * to move to the lifetime buffer. Make it 1k for the beginning.
+	 * to move to the lifetime buffer. Make it 4k for the beginning.
 	 */
 	return vregion_create(4096, buf_size - 4096);
 }

src/include/sof/audio/audio_buffer.h

@@ -60,6 +60,7 @@ struct audio_buffer_ops {
 				       const uint32_t frame_align_req);
 };
 
+struct mod_alloc_ctx;
 /* base class for all buffers, all buffers must inherit from it */
 struct sof_audio_buffer {
 	CORE_CHECK_STRUCT_FIELD;