Retire the synchronous character driver protocol

- change all sync char drivers into async drivers;
- retire support for the sync protocol in libchardev;
- remove async dev style, as this is now the default;
- remove dev_status from VFS;
- clean up now-unused protocol messages.

Change-Id: I6aacff712292f6b29f2ccd51bc1e7d7003723e87

drivers/random/main.c

@@ -59,7 +59,7 @@ int main(void)
   sef_local_startup();
 
   /* Call the generic receive loop. */
-  chardriver_task(&r_dtab, CHARDRIVER_ASYNC);
+  chardriver_task(&r_dtab);
 
   return(OK);
 }