boot: zephyr: add config for swap without scratch

Add Zephyr option to enable building a bootloader that uses an
alternative swap algorithm, that first moves up all sectors in slot1 and
then directly swaps between slot0 and slot1.

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/boot/zephyr/include/sysflash/sysflash.h b/boot/zephyr/include/sysflash/sysflash.h
index c422efd..25487ee 100644
--- a/boot/zephyr/include/sysflash/sysflash.h
+++ b/boot/zephyr/include/sysflash/sysflash.h
@@ -37,6 +37,8 @@
 #error "Image slot and flash area mapping is not defined"
 #endif
 
+#if !defined(CONFIG_BOOT_SWAP_USING_MOVE)
 #define FLASH_AREA_IMAGE_SCRATCH    DT_FLASH_AREA_IMAGE_SCRATCH_ID
+#endif
 
 #endif /* __SYSFLASH_H__ */