common: Move the image globals into image.h

These three globals relate to image handling. Move them to the image
header file.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/optee/optee.c b/lib/optee/optee.c
index c883c49..9b49eb8 100644
--- a/lib/optee/optee.c
+++ b/lib/optee/optee.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <image.h>
 #include <malloc.h>
 #include <linux/libfdt.h>
 #include <tee/optee.h>