netdev_upperhalf: add direct rx mode

avoid packet processing delays caused by task switching,
to support those applications that are extremely time-sensitive.

Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>

include/nuttx/net/netdev_lowerhalf.h

@@ -90,6 +90,7 @@ enum netpkt_type_e
 enum netdev_rx_e
 {
   NETDEV_RX_WORK,      /* Use work queue thread */
+  NETDEV_RX_DIRECT,    /* Directly based on the current thread */
   NETDEV_RX_THREAD,    /* Upper half dedicated thread */
   NETDEV_RX_THREAD_RSS /* RSS mode, upper half thread */
 };