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/MPC8548CDS.h b/include/configs/MPC8548CDS.h
index 6e44a07..de2bfd8 100644
--- a/include/configs/MPC8548CDS.h
+++ b/include/configs/MPC8548CDS.h
@@ -27,6 +27,7 @@
 #define CONFIG_FSL_VIA
 
 #ifndef __ASSEMBLY__
+#include <linux/stringify.h>
 extern unsigned long get_clock_freq(void);
 #endif
 #define CONFIG_SYS_CLK_FREQ	get_clock_freq() /* sysclk for MPC85xx */