boot: Order IMAGE_F_* flags defintions

Little cleanup.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
diff --git a/boot/bootutil/include/bootutil/image.h b/boot/bootutil/include/bootutil/image.h
index 90543b7..b8d0d07 100644
--- a/boot/bootutil/include/bootutil/image.h
+++ b/boot/bootutil/include/bootutil/image.h
@@ -50,8 +50,8 @@
  * Image header flags.
  */
 #define IMAGE_F_PIC                      0x00000001 /* Not supported. */
-#define IMAGE_F_NON_BOOTABLE             0x00000010 /* Split image app. */
 #define IMAGE_F_ENCRYPTED                0x00000004 /* Encrypted. */
+#define IMAGE_F_NON_BOOTABLE             0x00000010 /* Split image app. */
 /*
  * Indicates that this image should be loaded into RAM instead of run
  * directly from flash.  The address to load should be in the