GPU VA Manager To Land In Linux 6.6

The DRM subsystem is slated to pickup a GPU Virtual Address "VA" Manager with the Linux 6.6 kernel that is motivated by work around Vulkan sparse memory binding requirements.

Worked on by Red Hat, with testing and feedback from Intel and Imagination Tech and others, is the GPU VA Manager that provides the necessary infrastructure for helping to track GPU virtual address mappings. Particularly motivated around Vulkan sparse memory binding requirements, this generic manager can track GPU VA allocations and mappings, connect GPU VA mappings to their backing buffers, and provide a common implementation to perform mapping operations on the GPU VA space.

The GPU VA Manager went through many revisions while finally today it was submitted via drm-misc-next for queuing in DRM-Next until the upcoming Linux 6.6 merge window.

This pull request wires up the GPU VA Manager infrastructure so that DRM drivers can begin making use of it going forward. This pull also adds the DRM_IOCTL_SYNCOBJ_EVENTFD that is used ot register an eventfd that is useful such as for Wayland compositors to handle wait-before-submit events. WLROOTS has already been working on support for this ioctl to register an eventfd with the DRM synchronization object code.