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/net/bootp.c b/net/bootp.c
index 2c918d8..05bfede 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -9,6 +9,7 @@
  */
 
 #include <common.h>
+#include <bootstage.h>
 #include <command.h>
 #include <env.h>
 #include <efi_loader.h>