include: queue.h: Make flink clear after sq_rem

In the previous design, this member may be cleared or not cleared,
which results in the API's side effects not being a clear property.

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>

include/nuttx/queue.h

@@ -188,6 +188,10 @@
                 { \
                   (q)->tail = NULL; \
                 } \
+              else \
+                { \
+                  tmp_node->flink = NULL; \
+                } \
             } \
           else \
             { \