Bluetooth: Use memdup_user in le_auto_conn_write()

This patch does a small code simplification replacing the tipical
kmalloc-copy_from_user sequence by memdup_user() helper.

Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_core.c

@@ -955,14 +955,9 @@ static ssize_t le_auto_conn_write(struct file *file, const char __user *data,
 	if (count < 3)
 		return -EINVAL;
 
-	buf = kzalloc(count, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	if (copy_from_user(buf, data, count)) {
-		err = -EFAULT;
-		goto done;
-	}
+	buf = memdup_user(data, count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
 
 	if (memcmp(buf, "add", 3) == 0) {
 		n = sscanf(&buf[4], "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx %hhu %hhu",