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/board/mscc/serval/serval.c b/board/mscc/serval/serval.c
index 6c6dbf2..ed1aea5 100644
--- a/board/mscc/serval/serval.c
+++ b/board/mscc/serval/serval.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <image.h>
 #include <init.h>
 #include <asm/io.h>
 #include <led.h>