Restore erase in update_trigger.

Caveat: in case of powerfail during wolfBoot_update_trigger, the key
previously set may be lost. This is OK assuming that the update process
can resume from the previous step in the application (setting the key
before triggering the update).

Author: danielinux

src/libwolfboot.c

@@ -754,6 +754,7 @@ void RAMFUNCTION wolfBoot_update_trigger(void)
         lastSector -= selSec * WOLFBOOT_SECTOR_SIZE;
         XMEMCPY(NVM_CACHE, (uint8_t*)lastSector, WOLFBOOT_SECTOR_SIZE);
         /* write to the non selected sector */
+        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 */