doc: fix references to driver-model

Fix some errors pointed out by 'make refcheckdocs'.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index e53cf51..424d13f 100644
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -182,7 +182,7 @@
 
 The full device tree is available to U-Boot proper, but normally only a subset
 (or none at all) is available to TPL and SPL. See 'Pre-Relocation Support' and
-'SPL Support' in doc/driver-model/README.txt for more details.
+'SPL Support' in doc/driver-model/design.rst for more details.
 
 
 Using several DTBs in the SPL (CONFIG_SPL_MULTI_DTB)