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/sh/lib/bootm.c b/arch/sh/lib/bootm.c
index 2896e45..5f14a04 100644
--- a/arch/sh/lib/bootm.c
+++ b/arch/sh/lib/bootm.c
@@ -9,6 +9,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <image.h>
 #include <asm/byteorder.h>
 #include <asm/zimage.h>