Bluetooth: hci_h5: btrtl: Maintain flow control if wakeup is enabled

For chips that doesn't reset on suspend, we need to provide the correct
value of flow_control when it resumes. Therefore, store the flow
control value when reading from the config file to be reused upon
suspend.

Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Hilda Wu <hildawu@realtek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>