x86: dm: Mark driver model as dead when disabling CAR

When turning off CAR, set the flag to make sure that nothing tries to use
driver model in SPL before jumping to U-Bot proper, since its tables are
in CAR.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/lib/spl.c b/arch/x86/lib/spl.c
index 335dacf..c15f11f 100644
--- a/arch/x86/lib/spl.c
+++ b/arch/x86/lib/spl.c
@@ -230,6 +230,9 @@
 	mtrr_commit(false);
 	init_cache();
 	gd->flags &= ~GD_FLG_SERIAL_READY;
+
+	/* make sure driver model is not accessed from now on */
+	gd->flags |= GD_FLG_DM_DEAD;
 	debug("cache status %d\n", dcache_status());
 	board_init_r(gd, 0);
 }