Bluetooth: Fix crash in the Marvell driver initialization codepath

btmrvl_add_card() function calls kthread_run that might return error
(e.g. if current thread is killed). If one tries to use the error
value as a pointer then invalid memory access oops happens.

Check kthread_run() return value, if it is an error then release resources
correctly.

TEST=boot computer with BT modules enabled. I see the error message that
BT device initialization failed. Now kernel does not crash. Hint: to enable
BT run 'rmmod btmrvl_sdio; modprobe btmrvl_sdio'

Signed-off-by: Anatol Pomozov <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

drivers/bluetooth/btmrvl_main.c

···
 	init_waitqueue_head(&priv->main_thread.wait_q);
 	priv->main_thread.task = kthread_run(btmrvl_service_main_thread,
 				&priv->main_thread, "btmrvl_main_service");
+	if (IS_ERR(priv->main_thread.task))
+		goto err_thread;
 
 	priv->btmrvl_dev.card = card;
 	priv->btmrvl_dev.tx_dnld_rdy = true;
 
 	return priv;
+
+err_thread:
+	btmrvl_free_adapter(priv);
 
 err_adapter:
 	kfree(priv);