Fix call to pointing_device_handle_buttons

[0xcharly]

Description

pointing_device_handle_buttons(…) expects 3 arguments, the first one being an uint8_t corresponding to the report_mouse_t.buttons field to update.

Without this change, the ploopyco/trackball firmware fails to compile when MOUSEKEY_ENABLE is not defined.

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

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).

[daskygit]

Looks good to me, lines up with the trackball mini too.