drm/i915/display: Use intel_bo_to_drm_bo instead of obj->base

We are preparing for Xe. Xe_bo doesn't have obj->base. Due to this
use intel_bo_to_drm_bo instead in intel_prepare_plane_fb.
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231102112219.1039362-1-jouni.hogander@intel.com

drivers/gpu/drm/i915/display/intel_atomic_plane.c

@@ -1096,7 +1096,7 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
 		 * can safely continue.
 		 */
 		if (new_crtc_state && intel_crtc_needs_modeset(new_crtc_state)) {
-			ret = add_dma_resv_fences(old_obj->base.resv,
+			ret = add_dma_resv_fences(intel_bo_to_drm_bo(old_obj)->resv,
 						  &new_plane_state->uapi);
 			if (ret < 0)
 				return ret;