common: Drop image.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/spl/spl_legacy.c b/common/spl/spl_legacy.c
index 29d3ec7..db5017a 100644
--- a/common/spl/spl_legacy.c
+++ b/common/spl/spl_legacy.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <image.h>
 #include <malloc.h>
 #include <spl.h>