zephyr: allow to not defined scratch area in upgrade-only mode

Scratch area is unneeded if CONFIG_BOOT_SWAP_USING_SCRATCH=n.
This was not reflected so fare which causes build faliure.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/flash_map_extended.c b/boot/zephyr/flash_map_extended.c
index 7b6ae63..95b9506 100644
--- a/boot/zephyr/flash_map_extended.c
+++ b/boot/zephyr/flash_map_extended.c
@@ -59,9 +59,9 @@
     case 0: return FLASH_AREA_IMAGE_PRIMARY(image_index);
 #if !defined(CONFIG_SINGLE_APPLICATION_SLOT)
     case 1: return FLASH_AREA_IMAGE_SECONDARY(image_index);
-#if !defined(CONFIG_BOOT_SWAP_USING_MOVE)
-    case 2: return FLASH_AREA_IMAGE_SCRATCH;
 #endif
+#if defined(CONFIG_BOOT_SWAP_USING_SCRATCH)
+    case 2: return FLASH_AREA_IMAGE_SCRATCH;
 #endif
     }