bluetooth: hci_uart: remove unused hci_uart_init_tty

There are no users of hci_uart_init_tty, so remove it.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: linux-bluetooth@vger.kernel.org
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>