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/arch/arm/mach-keystone/mon.c b/arch/arm/mach-keystone/mon.c
index b7de9ba..58995d7 100644
--- a/arch/arm/mach-keystone/mon.c
+++ b/arch/arm/mach-keystone/mon.c
@@ -6,6 +6,7 @@
  */
 
 #include <hang.h>
+#include <image.h>
 #include <asm/unaligned.h>
 #include <common.h>
 #include <command.h>