hp-wmi: fix error path in hp_wmi_bios_setup()

The error-path code can call rfkill_unregister() with a pointer which does
not contain the result of a call to rfkill_register().  It goes BUG().

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=12560.

Cc: Frans Pop <elendil@planet.nl>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Len Brown <lenb@kernel.org>
Acked-by: NMatthew Garrett <mjg@redhat.com>
Reported-by: NHelge Deller <deller@gmx.de>
Testted-by: NHelge Deller <deller@gmx.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/platform/x86/hp-wmi.c

@@ -463,9 +463,11 @@ static int __init hp_wmi_bios_setup(struct platform_device *device)
 
 	return 0;
 register_wwan_err:
-	rfkill_unregister(bluetooth_rfkill);
+	if (bluetooth_rfkill)
+		rfkill_unregister(bluetooth_rfkill);
 register_bluetooth_error:
-	rfkill_unregister(wifi_rfkill);
+	if (wifi_rfkill)
+		rfkill_unregister(wifi_rfkill);
 add_sysfs_error:
 	cleanup_sysfs(device);
 	return err;