sandbox: Move the bloblist down a little in memory

Move this down by 4KB so that it is large enough to hold the devicetree.

Also fix up the devicetree address in the documetation while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/Kconfig b/common/Kconfig
index 21eaa5e..5e79b54 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -1012,7 +1012,7 @@
 
 config BLOBLIST_ADDR
 	hex "Address of bloblist"
-	default 0xc000 if SANDBOX
+	default 0xb000 if SANDBOX
 	depends on BLOBLIST_FIXED
 	help
 	  Sets the address of the bloblist, set up by the first part of U-Boot