drm/msm/dpu: Drop encoder vsync_event

drm/msm/dpu: Drop encoder vsync_event

Drop vsync_event and vsync_event_work handlers as they are unnecessary.
In addition drop the dpu_enc_ktime_template event class as it will be
unused after the vsync_event handlers are dropped.

Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/550983/
Link: https://lore.kernel.org/r/20230802-encoder-cleanup-v2-1-5bfdec0ce765@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>