README: fix openocd not finding files

README.md

@@ -40,12 +40,14 @@ Proceed using gdb with `load`, `c`
 
 ```shell
 nix-shell --command "cargo xbuild --release"
-openocd -f openocd/zc706.cfg
+cd openocd
+openocd -f zc706.cfg
 ```
 
 ### Running on the Cora Z7-10
 
 ```shell
 nix-shell --command "cargo xbuild --release --no-default-features --features=target_cora_z7_10"
-openocd -f openocd/cora-z7-10.cfg
+cd openocd
+openocd -f cora-z7-10.cfg
 ```