drm/msm/dpu: Remove unused code

Eliminate the follow clang warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c:544:33: warning: variable
‘mode’ set but not used [-Wunused-but-set-variable].

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Jiapeng Chong <[e-mail]>
Fixes: 3177589c6e93("drm/msm/dpu: encoder: drop unused mode_fixup callback")
Reviewed-by: Abhinav Kumar <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/487136/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Abhinav Kumar <[e-mail]>

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

···
 	struct dpu_encoder_virt *dpu_enc;
 	struct msm_drm_private *priv;
 	struct dpu_kms *dpu_kms;
-	const struct drm_display_mode *mode;
 	struct drm_display_mode *adj_mode;
 	struct msm_display_topology topology;
 	struct dpu_global_state *global_state;
···
 
 	priv = drm_enc->dev->dev_private;
 	dpu_kms = to_dpu_kms(priv->kms);
-	mode = &crtc_state->mode;
 	adj_mode = &crtc_state->adjusted_mode;
 	global_state = dpu_kms_get_global_state(crtc_state->state);
 	if (IS_ERR(global_state))