common: Drop bootstage.h from common header

Move this fairly uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>

common/bootstage.c

@@ -10,6 +10,7 @@
  */
 
 #include <common.h>
+#include <bootstage.h>
 #include <hang.h>
 #include <malloc.h>
 #include <sort.h>