fix zephyr target: corrupted build after zephyr PR #11180

zephyrproject-rtos/zephyr#11180: Zephyr target was corrupted as
recently zephyr's device tree started adding DT_ prefix in
generated labels.

This path aligns flash name macro used.


Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/include/target.h b/boot/zephyr/include/target.h
index 00251df..03e9098 100644
--- a/boot/zephyr/include/target.h
+++ b/boot/zephyr/include/target.h
@@ -33,7 +33,7 @@
 /*
  * Sanity check the target support.
  */
-#if !defined(FLASH_DEV_NAME) || \
+#if !defined(DT_FLASH_DEV_NAME) || \
     !defined(FLASH_ALIGN) ||                  \
     !defined(FLASH_AREA_IMAGE_0_OFFSET) || \
     !defined(FLASH_AREA_IMAGE_0_SIZE) || \