Bluetooth: Re-use kstrtobool_from_user()

Re-use kstrtobool_from_user() instead of open coded variant.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index a2ddae2..ae91e2d 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -3315,16 +3315,12 @@
 				     size_t count, loff_t *ppos)
 {
 	struct hci_dev *hdev = file->private_data;
-	char buf[32];
-	size_t buf_size = min(count, (sizeof(buf)-1));
 	bool enable;
+	int err;
 
-	if (copy_from_user(buf, user_buf, buf_size))
-		return -EFAULT;
-
-	buf[buf_size] = '\0';
-	if (strtobool(buf, &enable))
-		return -EINVAL;
+	err = kstrtobool_from_user(user_buf, count, &enable);
+	if (err)
+		return err;
 
 	if (enable == hci_dev_test_flag(hdev, HCI_FORCE_BREDR_SMP))
 		return -EALREADY;