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/km/km_arm.h b/include/configs/km/km_arm.h
index fa9d7b5..4e833fa 100644
--- a/include/configs/km/km_arm.h
+++ b/include/configs/km/km_arm.h
@@ -104,6 +104,7 @@
 
 #ifndef __ASSEMBLY__
 #include <asm/arch/gpio.h>
+#include <linux/stringify.h>
 extern void __set_direction(unsigned pin, int high);
 void set_sda(int state);
 void set_scl(int state);