drm/vkms: Run DRM default client setup

Call drm_client_setup() 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

Signed-off-by: Thomas Zimmermann <[e-mail]>
Cc: Rodrigo Siqueira <[e-mail]>
Cc: Melissa Wen <[e-mail]>
Cc: "Maíra Canal" <[e-mail]>
Cc: Haneen Mohammed <[e-mail]>
Acked-by: Javier Martinez Canillas <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/vkms/Kconfig

···
 config DRM_VKMS
 	tristate "Virtual KMS (EXPERIMENTAL)"
 	depends on DRM && MMU
+	select DRM_CLIENT_SELECTION
 	select DRM_KMS_HELPER
 	select DRM_GEM_SHMEM_HELPER
 	select CRC32

drivers/gpu/drm/vkms/vkms_drv.c

···
 #include <drm/drm_gem.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_client_setup.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_fbdev_shmem.h>
 #include <drm/drm_file.h>
···
 	.release		= vkms_release,
 	.fops			= &vkms_driver_fops,
 	DRM_GEM_SHMEM_DRIVER_OPS,
+	DRM_FBDEV_SHMEM_DRIVER_OPS,
 
 	.name			= DRIVER_NAME,
 	.desc			= DRIVER_DESC,
···
 	if (ret)
 		goto out_devres;
 
-	drm_fbdev_shmem_setup(&vkms_device->drm, 0);
+	drm_client_setup(&vkms_device->drm, NULL);
 
 	return 0;