net/arp: Redesign ARP table aging to simplify the net initialization

include/nuttx/net/arp.h

@@ -83,7 +83,7 @@ struct arp_entry_s
 {
   in_addr_t         at_ipaddr;   /* IP address */
   struct ether_addr at_ethaddr;  /* Hardware address */
-  uint8_t           at_time;     /* Time of last usage */
+  clock_t           at_time;     /* Time of last usage */
 };
 
 /* Used with the SIOCSARP, SIOCDARP, and SIOCGARP IOCTL commands to set,

include/nuttx/net/net.h

@@ -256,7 +256,7 @@ extern "C"
  ****************************************************************************/
 
 /****************************************************************************
- * Name: net_setup
+ * Name: net_initialize
  *
  * Description:
  *   This is called from the OS initialization logic at power-up reset in
@@ -278,25 +278,6 @@ extern "C"
  *
  ****************************************************************************/
 
-void net_setup(void);
-
-/****************************************************************************
- * Name: net_initialize
- *
- * Description:
- *   This function is called from the OS initialization logic at power-up
- *   reset AFTER initialization of hardware facilities such as timers and
- *   interrupts.   This logic completes the initialization started by
- *   net_setup().
- *
- * Input Parameters:
- *   None
- *
- * Returned Value:
- *   None
- *
- ****************************************************************************/
-
 void net_initialize(void);
 
 /****************************************************************************