kernel: Reapply "drm/qxl: simplify qxl_fence_wait"

In the Linux kernel, the following vulnerability has been resolved: Reapply "drm/qxl: simplify qxlfencewait" This reverts commit 07ed11afb68d94eadd4ffc082b97c2331307c5ea. Stephen Rostedt reports: "I went to run my tests on my VMs and the tests hung on boot up. Unfortunately, the most I ever got o...