common: Drop linux/stringify.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/env_default.h b/include/env_default.h
index 56a8bae..a657927 100644
--- a/include/env_default.h
+++ b/include/env_default.h
@@ -8,6 +8,7 @@
  */
 
 #include <env_callback.h>
+#include <linux/stringify.h>
 
 #ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
 env_t embedded_environment __UBOOT_ENV_SECTION__(environment) = {