ci: bump kernel to 6.6.16 + enable X2APIC

What does this MR do and why?

ci: bump kernel to 6.6.16 + enable X2APIC

Should lead to slightly better reliability + eventual performance boost
on Intel HW.

Also reverted:

 - `ae795abe7b3e ("drm/msm/dsi: Use pm_runtime_resume_and_get to prevent refcnt leaks")`
 - `78a1eb102c7f ("drm/msm/dsi: Enable runtime PM")`

so a306 testing won't break.

Signed-off-by: David Heidelberg <david.heidelberg@collabora.com>