Documentation - fix warnings

Building IGT documentation spews out a lot of warnings:

• missing symbol name at the start of the comment block
• issues with parameter descriptions
• missing links for symbols

Someone should work with library authors to fix them and make sure that everything builds cleanly.

This can (and possibly should) be done over multiple patches and can be done by more than one person. If necessary sub-issues can be created.

Resources:

• https://gitlab.freedesktop.org/drm/igt-gpu-tools/blob/master/README.md#docs
• https://drm.pages.freedesktop.org/igt-gpu-tools/
• https://gitlab.freedesktop.org/drm/igt-gpu-tools/tree/master/docs/reference/igt-gpu-tools