drm/msm/dpu: drop MSM_ENC_VBLANK support

There are no in-kernel users of MSM_ENC_VBLANK wait type. Drop it
together with the corresponding wait_for_vblank callback.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/560701/
Link: https://lore.kernel.org/r/20231004031903.518223-1-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>