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>
diff --git a/board/Seagate/goflexhome/goflexhome.c b/board/Seagate/goflexhome/goflexhome.c
index 1e4477a..fd2f0df 100644
--- a/board/Seagate/goflexhome/goflexhome.c
+++ b/board/Seagate/goflexhome/goflexhome.c
@@ -12,6 +12,7 @@
  */
 
 #include <common.h>
+#include <bootstage.h>
 #include <miiphy.h>
 #include <net.h>
 #include <asm/mach-types.h>