drm/msm/dpu: remove dpu_encoder_virt_ops

Struct dpu_encoder_virt_ops is used to provide several callbacks to the
phys_enc backends. However these ops are static and are not supposed to
change in the foreseeble future. Drop the indirection and call
corresponding functions directly.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/516518/
Link: https://lore.kernel.org/r/20230102154748.951328-1-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>