stop the selSec from being applied twice to lastSector

Author: jpbland1

src/libwolfboot.c

@@ -763,10 +763,11 @@ void RAMFUNCTION wolfBoot_update_trigger(void)
         hal_flash_erase(lastSector, SECTOR_FLAGS_SIZE);
 #else
         selSec = nvm_select_fresh_sector(PART_UPDATE);
-        lastSector -= selSec * WOLFBOOT_SECTOR_SIZE;
-        XMEMCPY(NVM_CACHE, (uint8_t*)lastSector, WOLFBOOT_SECTOR_SIZE);
+        XMEMCPY(NVM_CACHE, (uint8_t*)lastSector - WOLFBOOT_SECTOR_SIZE * selSec,
+            WOLFBOOT_SECTOR_SIZE);
         /* write to the non selected sector */
-        hal_flash_erase(lastSector - WOLFBOOT_SECTOR_SIZE * !selSec, WOLFBOOT_SECTOR_SIZE);
+        hal_flash_erase(lastSector - WOLFBOOT_SECTOR_SIZE * !selSec,
+            WOLFBOOT_SECTOR_SIZE);
         hal_flash_write(lastSector - WOLFBOOT_SECTOR_SIZE * !selSec, NVM_CACHE,
             WOLFBOOT_SECTOR_SIZE);
         /* erase the previously selected sector */