Fix typo in ghdl/vcd example
@@ -384,7 +384,7 @@ The option can be set on the command line, as shown in the following example.
.. code-block:: bash
- SIM_ARGS=--vcd=anyname.vhd make SIM=ghdl
+ SIM_ARGS=--vcd=anyname.vcd make SIM=ghdl
A VCD file named :file:`anyname.vcd` will be generated in the current directory.
