README: Fix typo in description of CONFIG_OF_EMBED

The correct name is 'gd->fdt_blob', not 'gd->blob'.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
CC: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/README b/README
index fc40ddf..a46850c 100644
--- a/README
+++ b/README
@@ -776,7 +776,7 @@
 		binary in its image. This device tree file should be in the
 		board directory and called <soc>-<board>.dts. The binary file
 		is then picked up in board_init_f() and made available through
-		the global data structure as gd->blob.
+		the global data structure as gd->fdt_blob.
 
 		CONFIG_OF_SEPARATE
 		If this variable is defined, U-Boot will build a device tree