bluetooth: hci: ipc: assert when building HCI IPC driver w/o ACL FC

The HCI IPC driver is not reliable and can lead to lost ACL data if
built without Controller-to-Host ACL flow control.

This commit prevents building HCI IPC driver and hci_ipc sample without
CONFIG_BT_HCI_ACL_FLOW_CONTROL.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>