Add ftruncate into file operation calls

- Add truncate into file_operations
- Move truncate to be common for mountpt_operations and file_operations
- Modify all drivers to initialize the operations struct accordingly

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

fs/socket/socket.c

@@ -64,6 +64,7 @@ static const struct file_operations g_sock_fileops =
   sock_file_write,  /* write */
   NULL,             /* seek */
   sock_file_ioctl,  /* ioctl */
+  NULL,             /* truncate */
   sock_file_poll    /* poll */
 #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
   , NULL            /* unlink */