doc: typo fdtaddr_addr_r

%s/fdtaddr_addr_r/fdt_addr_r/

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/develop/bootstd.rst b/doc/develop/bootstd.rst
index 51cd573..496e24b 100644
--- a/doc/develop/bootstd.rst
+++ b/doc/develop/bootstd.rst
@@ -247,7 +247,7 @@
     Name of the flattened device tree (FDT) file to load, e.g.
     "rockchip/rk3399-rockpro64.dtb"
 
-fdtaddr_addr_r
+fdt_addr_r
     Address at which to load the FDT, e.g. 0x01f00000
 
 fdtoverlay_addr_r (needed if overlays are used)