Move a comment to the right place in tor_zstd_compress_process

Part of #22502

src/common/compress_zstd.c

@@ -312,6 +312,8 @@ tor_zstd_compress_process(tor_zstd_compress_state_t *state,
       return TOR_COMPRESS_ERROR;
     }
 
+    // ZSTD_flushStream returns 0 if the frame is done, or >0 if it
+    // is incomplete.
     if (retval > 0)
       return TOR_COMPRESS_BUFFER_FULL;
   }
@@ -339,8 +341,6 @@ tor_zstd_compress_process(tor_zstd_compress_state_t *state,
 
     return TOR_COMPRESS_DONE;
   } else {
-    // ZSTD_flushStream returns 0 if the frame is done, or >0 if it
-    // is incomplete.
     return (retval == 0) ? TOR_COMPRESS_DONE : TOR_COMPRESS_OK;
   }