sched/wdog: remove unnecessary list_node redefinition

The wdog implementation redefined `list_node`, which could cause
  conflicts or unexpected behavior when both `wdog/wdog.h` and
  `list.h` are included in the same source file. This patch removes
  the redundant definition to avoid such issues.

Signed-off-by: Chengdong Wang <wangchengdong@lixiang.com>

include/nuttx/wdog.h

@@ -31,6 +31,7 @@
 
 #include <nuttx/compiler.h>
 #include <nuttx/clock.h>
+#include <nuttx/list.h>
 #include <errno.h>
 #include <stdint.h>
 
@@ -78,19 +79,11 @@ typedef uint32_t  wdparm_t;
 
 typedef CODE void (*wdentry_t)(wdparm_t arg);
 
-/* Avoid the inclusion of nuttx/list.h */
-
-struct wdlist_node
-{
-  FAR struct wdlist_node *prev;
-  FAR struct wdlist_node *next;
-};
-
 /* Support a doubly linked list of watchdog timers */
 
 struct wdog_s
 {
-  struct wdlist_node node;       /* Supports a doubly linked list */
+  struct list_node  node;        /* Supports a doubly linked list */
   wdparm_t           arg;        /* Callback argument */
   wdentry_t          func;       /* Function to execute when delay expires */
 #ifdef CONFIG_PIC

sched/wdog/wdog.h

@@ -36,17 +36,12 @@
 #include <nuttx/clock.h>
 #include <nuttx/queue.h>
 #include <nuttx/wdog.h>
-#include <nuttx/list.h>
 #include <nuttx/spinlock_type.h>
 
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
 
-/* Redefine to the standard list */
-
-#define list_node wdlist_node
-
 /****************************************************************************
  * Public Data
  ****************************************************************************/