global_data: Convert have_console into a flag

We don't need a full word for this boolean value. Convert it into a flag
to save space in global_data.

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/siemens/common/board_am335x.c b/board/siemens/common/board_am335x.c
index 2a72760..e6537b0 100644
--- a/board/siemens/common/board_am335x.c
+++ b/board/siemens/common/board_am335x.c
@@ -36,7 +36,7 @@
 	/* enable early the console */
 	gd->baudrate = CONFIG_BAUDRATE;
 	serial_init();
-	gd->have_console = 1;
+	gd->flags |= GD_FLG_HAVE_CONSOLE;
 
 	siemens_ee_setup();
 	if (draco_read_eeprom() < 0)