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

Remove custom qxl_init() and qxl_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/qxl/qxl_drv.c

···
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
 #include <drm/drm_gem_ttm_helper.h>
+#include <drm/drm_module.h>
 #include <drm/drm_modeset_helper.h>
 #include <drm/drm_prime.h>
 #include <drm/drm_probe_helper.h>
···
 	.release = qxl_drm_release,
 };
 
-static int __init qxl_init(void)
-{
-	if (drm_firmware_drivers_only() && qxl_modeset == -1)
-		return -EINVAL;
-
-	if (qxl_modeset == 0)
-		return -EINVAL;
-	return pci_register_driver(&qxl_pci_driver);
-}
-
-static void __exit qxl_exit(void)
-{
-	pci_unregister_driver(&qxl_pci_driver);
-}
-
-module_init(qxl_init);
-module_exit(qxl_exit);
+drm_module_pci_driver_if_modeset(qxl_pci_driver, qxl_modeset);
 
 MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);