drm/msm/dpu: move dpu_encoder's connector assignment to atomic_enable()

For cases where the crtc's connectors_changed was set without enable/active
getting toggled , there is an atomic_enable() call followed by an
atomic_disable() but without an atomic_mode_set().

This results in a NULL ptr access for the dpu_encoder_get_drm_fmt() call in
the atomic_enable() as the dpu_encoder's connector was cleared in the
atomic_disable() but not re-assigned as there was no atomic_mode_set() call.

Fix the NULL ptr access by moving the assignment for atomic_enable() and also
use drm_atomic_get_new_connector_for_encoder() to get the connector from
the atomic_state.

Fixes: 25fdd593 ("drm/msm: Add SDM845 DPU support")
Reported-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/59Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> # SM8350-HDK
Patchwork: https://patchwork.freedesktop.org/patch/606729/
Link: https://lore.kernel.org/r/20240731191723.3050932-1-quic_abhinavk@quicinc.comSigned-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c

@@ -1171,8 +1171,6 @@ static void dpu_encoder_virt_atomic_mode_set(struct drm_encoder *drm_enc,
 
 	cstate->num_mixers = num_lm;
 
-	dpu_enc->connector = conn_state->connector;
-
 	for (i = 0; i < dpu_enc->num_phys_encs; i++) {
 		struct dpu_encoder_phys *phys = dpu_enc->phys_encs[i];
 
@@ -1270,6 +1268,8 @@ static void dpu_encoder_virt_atomic_enable(struct drm_encoder *drm_enc,
 
 	dpu_enc->commit_done_timedout = false;
 
+	dpu_enc->connector = drm_atomic_get_new_connector_for_encoder(state, drm_enc);
+
 	cur_mode = &dpu_enc->base.crtc->state->adjusted_mode;
 
 	dpu_enc->wide_bus_en = dpu_encoder_is_widebus_enabled(drm_enc);