env: export fdt_blob to the environment variable

Export fdt_blob to the environment variable. So that we may
use it to boot Linux.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Simon Glass <sjg@chromium.org>

common/board_r.c

@@ -446,6 +446,9 @@ static int initr_env(void)
 		env_relocate();
 	else
 		set_default_env(NULL);
+#ifdef CONFIG_OF_CONTROL
+	setenv_addr("fdtcontroladdr", gd->fdt_blob);
+#endif
 
 	/* Initialize from environment */
 	load_addr = getenv_ulong("loadaddr", 16, load_addr);

doc/README.fdt-control

@@ -156,7 +156,10 @@ address of the fdt binary blob, and will override either of the options.
 Be aware that this environment variable is checked prior to relocation,
 when only the compiled-in environment is available. Therefore it is not
 possible to define this variable in the saved SPI/NAND flash
-environment, for example (it will be ignored).
+environment, for example (it will be ignored). After relocation, this
+variable will be set to the address of the newly relocated fdt blob.
+It is read-only and cannot be changed. It can optionally be used to
+control the boot process of Linux with bootm/bootz commands.
 
 To use this, put something like this in your board header file: