- Put 'D' before other params for clean exit.
- Use serial on/off for debug status.

M303 D will now toggle activation of PID_DEBUG output.   This allows the debug capability to be built into the firmware, but turned on and off as needed.

The code is slightly more optimized than it used to be and this has caused the setup and hold times on the Formbot T-Rex 2+ machines to be insufficient.   This change gives sufficient margin and the LCD Display is clean again.

Something has shifted.   The previous timing delays on the Max7219 debug displays is too tight without this correction.
I suspect something has been optimized and roughly 50ns of needed setup and hold time has disappeared.
This corrects the issue and the display results are clean again.

Co-authored-by: Scott Lahteine <github@thinkyhead.com>

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Fixes #17255

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Followup to #17149