drm/xlnx: Run DRM default client setup

Call drm_client_setup_with_fourcc() to run the kernel's default client
setup for DRM. Set fbdev_probe in struct drm_driver, so that the client
setup can start the common fbdev client.

v5:
- select DRM_CLIENT_SELECTION
v2:
- use drm_client_setup_with_fourcc()

Signed-off-by: Thomas Zimmermann <[e-mail]>
Cc: Laurent Pinchart <[e-mail]>
Cc: Tomi Valkeinen <[e-mail]>
Cc: Michal Simek <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/xlnx/Kconfig

···
 	depends on PHY_XILINX_ZYNQMP
 	depends on XILINX_ZYNQMP_DPDMA
 	select DMA_ENGINE
+	select DRM_CLIENT_SELECTION
 	select DRM_DISPLAY_DP_HELPER
 	select DRM_DISPLAY_HELPER
 	select DRM_BRIDGE_CONNECTOR

drivers/gpu/drm/xlnx/zynqmp_kms.c

···
 #include <drm/drm_blend.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_bridge_connector.h>
+#include <drm/drm_client_setup.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_device.h>
···
 					  DRIVER_ATOMIC,
 
 	DRM_GEM_DMA_DRIVER_OPS_WITH_DUMB_CREATE(zynqmp_dpsub_dumb_create),
+	DRM_FBDEV_DMA_DRIVER_OPS,
 
 	.fops				= &zynqmp_dpsub_drm_fops,
 
···
 		goto err_poll_fini;
 
 	/* Initialize fbdev generic emulation. */
-	drm_fbdev_dma_setup(drm, 24);
+	drm_client_setup_with_fourcc(drm, DRM_FORMAT_RGB888);
 
 	return 0;