UBUNTU-CVE-2026-80915: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: drm/xe: Fix DPT allocation paths. Remove the fallback for VRAM to system memory, I tested it and that doesn't work at all, only a black screen with pipe fault errors were observed. On systems with media GT, extra latency is added when accessing stolen memory when the GT is in MC6. Since we additionally aren't counting how much memory is used for stolen and we could in theory fill up the entire stolen area with DPT's, avoid using stolen and only use the default memory region. Using stolen may also result in random system hangs under load. (cherry picked from commit a196406a3831291598fe8e73245914f7acffdfe0)