Fixed MCO (Master Clock Output) functionality. This was broken with changes made in version 2.0

Bugs:

1. Setting PA8 pin as MCO from LQFP64 window or Pinout window had no effect on Clock window.

2. Having PA8 pin function set to other than “N/A” or “CLOCK”, entering in Clock window would have re-set the pin function to “N/A”.

These are fixed. You can see the changes here https://gitlab.com/funlw65/vscode_nucleo_l152re/commit/d213bf77