Bluetooth: hci_qca: Remove serdev_device_open/close function calls

Removed serdev_device_open/close functions from qca_open/close as
they are called in hci_uart_register_device() and
hci_uart_unregister_device() functions.

Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>