Bluetooth: hci_h5: directly return hci_uart_register_device() ret-val

Since the hci_uart_register_device() call is the last thing we do in
h5_serdev_probe() we can simply directly return its return-value.

Cc: Archie Pusaka <apusaka@google.com>
Suggested-by: Archie Pusaka <apusaka@google.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>