The frame event callback is always set to dpu_crtc_frame_event_cb() (or
to NULL) and the data is always either the CRTC itself or NULL
(correpondingly). Thus drop the event callback registration, call the
dpu_crtc_frame_event_cb() directly and gate on the dpu_enc->crtc
assigned using dpu_encoder_assign_crtc().

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/600751/
Link: https://lore.kernel.org/r/20240625-dpu-no-crtc-register-v3-1-1b161df13776@linaro.org