drm/xlnx: Do not include <drm/drm_plane_helper.h>

Remove unnecessary include statements for <drm/drm_plane_helper.h>.
The file contains helpers for non-atomic code and should not be
required by most drivers. No functional changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231204090852.1650-9-tzimmermann@suse.de

drivers/gpu/drm/xlnx/zynqmp_kms.c

@@ -27,7 +27,6 @@
 #include <drm/drm_managed.h>
 #include <drm/drm_mode_config.h>
 #include <drm/drm_plane.h>
-#include <drm/drm_plane_helper.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_simple_kms_helper.h>
 #include <drm/drm_vblank.h>