samples: Bluetooth: hci_rpmsg: Fix Broadcast and Sync Receiver prj conf

Fix Broadcast ISO and Synchronized Receiver project
configurations related to IPC use.

Relates to commit cf6a58d3 ("bluetooth: hci: rpmsg:
use ipc service library").

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>