Revert "Use board's last flash sector for eeprom storage"

This reverts commit e31d3c1, because it
seems to cause trouble with the OTAA join process. If left in, the join
process results in:

	Initilizating LoRaWAN ...
	DevEui      : XX-XX-XX-XX-XX-XX-XX-XX
	JoinEui     : 00-00-00-00-00-00-00-00
	Pin         : 00-00-00-00

	success!
	Joining LoRaWAN network ...
	###### =========== MLME-Request ============ ######
	######               MLME_JOIN               ######
	###### ===================================== ######
	STATUS      : Duty-cycle restricted
	Next Tx in  : 3599930 [ms]

Reason: Still unknown. The join process works without those new eeprom
features.

Author: ThomasLeister

src/boards/rp2040/eeprom-board.c

@@ -5,47 +5,15 @@
  * 
  */
 
-#include <string.h>
-
-#include "pico/stdlib.h"
-#include "hardware/flash.h"
-
 #include "utilities.h"
 #include "eeprom-board.h"
 
-#define EEPROM_SIZE    (FLASH_SECTOR_SIZE)
-#define EEPROM_OFFSET  (PICO_FLASH_SIZE_BYTES - EEPROM_SIZE)
-#define EEPROM_ADDRESS ((const uint8_t*)(XIP_BASE + EEPROM_OFFSET))
-
-static uint8_t eeprom_write_cache[EEPROM_SIZE];
-
-void EepromMcuInit()
-{
-    memcpy(eeprom_write_cache, EEPROM_ADDRESS, sizeof(eeprom_write_cache));
-}
-
 uint8_t EepromMcuReadBuffer( uint16_t addr, uint8_t *buffer, uint16_t size )
 {
-    memcpy(buffer, EEPROM_ADDRESS + addr, size);
-    
-    return SUCCESS;
+    return FAIL;
 }
 
 uint8_t EepromMcuWriteBuffer( uint16_t addr, uint8_t *buffer, uint16_t size )
 {
-    memcpy(eeprom_write_cache + addr, buffer, size);
-
-    return SUCCESS;
-}
-
-uint8_t EepromMcuFlush()
-{
-    uint32_t mask;
-
-    BoardCriticalSectionBegin(&mask);
-
-    flash_range_erase(EEPROM_OFFSET, sizeof(eeprom_write_cache));
-    flash_range_program(EEPROM_OFFSET, eeprom_write_cache, sizeof(eeprom_write_cache));
-
-    BoardCriticalSectionEnd(&mask);
+    return FAIL;
 }

src/lorawan.c

@@ -185,9 +185,6 @@ static LmHandlerAppData_t AppRxData =
 
 static bool Debug = false;
 
-extern void EepromMcuInit();
-extern uint8_t EepromMcuFlush();
-
 const char* lorawan_default_dev_eui(char* dev_eui)
 {
     uint8_t boardId[8];
@@ -205,8 +202,6 @@ const char* lorawan_default_dev_eui(char* dev_eui)
 
 static int lorawan_init(const struct lorawan_sx12xx_settings* sx12xx_settings, LoRaMacRegion_t region)
 {
-    EepromMcuInit();
-
     RtcInit();
 #if defined sx1276 
     SpiInit(
@@ -395,8 +390,6 @@ static void OnNvmDataChange( LmHandlerNvmContextStates_t state, uint16_t size )
     if (Debug) {
         DisplayNvmDataChange( state, size );
     }
-
-    EepromMcuFlush();
 }
 
 static void OnNetworkParametersChange( CommissioningParams_t* params )