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/MPC8544DS.h b/include/configs/MPC8544DS.h
index 2092e3d..c9f193f 100644
--- a/include/configs/MPC8544DS.h
+++ b/include/configs/MPC8544DS.h
@@ -22,6 +22,7 @@
 #define CONFIG_INTERRUPTS		/* enable pci, srio, ddr interrupts */
 
 #ifndef __ASSEMBLY__
+#include <linux/stringify.h>
 extern unsigned long get_board_sys_clk(unsigned long dummy);
 #endif
 #define CONFIG_SYS_CLK_FREQ	get_board_sys_clk(0) /* sysclk for MPC85xx */