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/lib/time.c b/lib/time.c
index 75de48f..1395f28 100644
--- a/lib/time.c
+++ b/lib/time.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <bootstage.h>
 #include <dm.h>
 #include <errno.h>
 #include <time.h>