Bluetooth: hci_uart: Make struct hci_uart_proto always const

The usage of struct hci_uart_proto should always be const. Change the
function headers and individual protocol drivers.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

diff --cc drivers/bluetooth/hci_ath.c
Simple merge

diff --cc drivers/bluetooth/hci_bcsp.c
Simple merge

diff --cc drivers/bluetooth/hci_h4.c
Simple merge

diff --cc drivers/bluetooth/hci_h5.c
Simple merge

diff --cc drivers/bluetooth/hci_ldisc.c
Simple merge

diff --cc drivers/bluetooth/hci_ll.c
Simple merge

diff --cc drivers/bluetooth/hci_uart.h
Simple merge