Since commit 49dba410a730 ("drm/vkms: Bugfix racing hrtimer vblank
handle") the work is scheduled at vkms_vblank_simulate() and since
commit 45fdc1e0993c ("drm/vkms: flush crc workers earlier in commit
flow") the work is flushed at vkms_atomic_commit_tail(). Update function
commment to reflect that.