Fix PS/2 Trackpoint mouse clicks (#22265)

[strobo5]

Description

Bug report #22265 and fix by d93921012, I'm just pushing the change. There is a longer description the bug report; shorter summary:

When the main loop calls ps2_mouse_task() for the first time after the button down event, it finds no new data in the PS/2 receive buffer. Here it should return, or it tries to detect a button state change anyway and updates the mouse state with the button released before it is actually released. When doing click and drag, it cycles between button down and up.

Tested on ARM ChibiOS (RP2040) with a Trackpoint from a Thinkpad T61. With this change it works perfectly. The keyboard itself is a home-made converter for the Thinkpad keyboard (only in my personal fork at this point).

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• Fixes [Bug] Trackpoint work improperly in Interrupt Version (ARM chibios) PS/2 Mouse Support  #22265

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[drashna]

This also should probably be targeting the develop branch.

[zvecr]

Bugfix, so it could go directly to master however theres no harm in it going to develop given the cycles timeframe.