components: lwip - Modify lwip task priority and stack definition method

lwip task priority and stack size defintion should not depends on esp_task.h, define it
in lwipopts.h directly

components/lwip/include/lwip/port/lwipopts.h

@@ -33,7 +33,6 @@
 #define __LWIPOPTS_H__
 
 #include <stdlib.h>
-#include "esp_task.h"
 
 /* Enable all Espressif-only options */
 #define LWIP_ESP8266
@@ -324,14 +323,14 @@ extern unsigned char misc_prof_get_tcp_snd_buf(void);
  * The stack size value itself is platform-dependent, but is passed to
  * sys_thread_new() when the thread is created.
  */
-#define TCPIP_THREAD_STACKSIZE          ESP_TASKD_LWIP_STACK
+#define TCPIP_THREAD_STACKSIZE          2048
 
 /**
  * TCPIP_THREAD_PRIO: The priority assigned to the main tcpip thread.
  * The priority value itself is platform-dependent, but is passed to
  * sys_thread_new() when the thread is created.
  */
-#define TCPIP_THREAD_PRIO               ESP_TASKD_LWIP_PRIO
+#define TCPIP_THREAD_PRIO               (configMAX_PRIORITIES - 7)
 
 /**
  * TCPIP_MBOX_SIZE: The mailbox size for the tcpip thread messages