Fix wolfBoot_update_trigger sector calculation

wolfBoot_update_trigger is called to initiate an update on the next
boot. It does this by modifying the metadata in the last sector
(selecting one of the two if NVM_FLASH_WRITEONCE is defined).

There's a check to handle the case where the PART_UPDATE_ENDFLAGS isn't
aligned with the WOLFBOOT_SECTOR_SIZE. However, this check was wrong, as
the modulo of these two macros is 0 when aligned, so the check should be
!= 0.

src/libwolfboot.c

@@ -742,7 +742,7 @@ void RAMFUNCTION wolfBoot_update_trigger(void)
 
     /* if PART_UPDATE_ENDFLAGS straddles a sector, (all non FLAGS_HOME builds)
      * align it to the correct sector */
-    if (PART_UPDATE_ENDFLAGS % WOLFBOOT_SECTOR_SIZE == 0)
+    if (PART_UPDATE_ENDFLAGS % WOLFBOOT_SECTOR_SIZE != 0)
         lastSector -= WOLFBOOT_SECTOR_SIZE;
 
     /* erase the sector flags */