Restore some openocd information which I occassionally need.
This is a partial revert of:
```
commit 58a5e0744b
Author: Abdelatif Guettouche <abdelatif.guettouche@espressif.com>
Date: Mon Jul 26 21:43:42 2021 +0200
Documentation/esp32: Remove the rest of the OpenOCD text.
This information there is outdated and some of its content should be in
the board documentation and not the chip.
Signed-off-by: Abdelatif Guettouche <abdelatif.guettouche@espressif.com>
```
2e0de13813