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/configs/vf610twr.h b/include/configs/vf610twr.h
index 739219e..0ef2de3 100644
--- a/include/configs/vf610twr.h
+++ b/include/configs/vf610twr.h
@@ -9,6 +9,7 @@
 #define __CONFIG_H
 
 #include <asm/arch/imx-regs.h>
+#include <linux/stringify.h>
 
 #define CONFIG_SYS_FSL_CLK