drm/xlnx: Don't set struct drm_device.irq_enabled

The field drm_device.irq_enabled is only used by legacy drivers
with userspace modesetting. Don't set it in xlnx.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Acked-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/xlnx/zynqmp_dpsub.c

···
 	if (ret)
 		return ret;
 
-	drm->irq_enabled = 1;
-
 	drm_kms_helper_poll_init(drm);
 
 	/*