Add macros for image ok values
diff --git a/boot/bootutil/src/bootutil_priv.h b/boot/bootutil/src/bootutil_priv.h
index 45ce625..925e7f3 100644
--- a/boot/bootutil/src/bootutil_priv.h
+++ b/boot/bootutil/src/bootutil_priv.h
@@ -90,6 +90,9 @@
 #define BOOT_FLAG_IMAGE_OK         0
 #define BOOT_FLAG_COPY_DONE        1
 
+#define BOOT_IMAGE_OK              0x01
+#define BOOT_IMAGE_UNSET           0xff
+
 extern const uint32_t BOOT_MAGIC_SZ;
 
 int bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, int slen,