drm/vboxvideo: Replace module-init boiler-plate code with DRM helpers

Remove custom vbox_init() and vbox_exit() functions and initialize
the module with DRM module helpers.

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

drivers/gpu/drm/vboxvideo/vbox_drv.c

···
 #include <drm/drm_file.h>
 #include <drm/drm_ioctl.h>
 #include <drm/drm_managed.h>
+#include <drm/drm_module.h>
 
 #include "vbox_drv.h"
 
···
 	DRM_GEM_VRAM_DRIVER,
 };
 
-static int __init vbox_init(void)
-{
-	if (drm_firmware_drivers_only() && vbox_modeset == -1)
-		return -EINVAL;
-
-	if (vbox_modeset == 0)
-		return -EINVAL;
-
-	return pci_register_driver(&vbox_pci_driver);
-}
-
-static void __exit vbox_exit(void)
-{
-	pci_unregister_driver(&vbox_pci_driver);
-}
-
-module_init(vbox_init);
-module_exit(vbox_exit);
+drm_module_pci_driver_if_modeset(vbox_pci_driver, vbox_modeset);
 
 MODULE_AUTHOR("Oracle Corporation");
 MODULE_AUTHOR("Hans de Goede <[e-mail]>");