ALSA: riptide - proper handling of pci_register_driver for joystick

We need to check returning error for pci_register_driver(&joystick_driver)

On failure, we should unregister formerly registered audio drivers

This also fixed the compiler warning :

CC [M] sound/pci/riptide/riptide.o
sound/pci/riptide/riptide.c: In function ‘alsa_card_riptide_init’:
sound/pci/riptide/riptide.c:2200: warning: ignoring return value of ‘__pci_register_driver’, declared with attribute warn_unused_result

Signed-off-by: Jaswinder Singh Rajput <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/pci/riptide/riptide.c

···
 	if (err < 0)
 		return err;
 #if defined(SUPPORT_JOYSTICK)
-	pci_register_driver(&joystick_driver);
+	err = pci_register_driver(&joystick_driver);
+	/* On failure unregister formerly registered audio driver */
+	if (err < 0)
+		pci_unregister_driver(&driver);
 #endif
-	return 0;
+	return err;
 }
 
 static void __exit alsa_card_riptide_exit(void)