samples: fast_pair: input_device: Fix build failures on nRF5340 DK

Change brings back hci_ipc configuration used for child images to fix
build errors on nRF5340 DK.

Jira: NCSDK-27508

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>

Author: MarekPieta

samples/bluetooth/fast_pair/input_device/sysbuild/hci_ipc.conf

@@ -0,0 +1,8 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+# The sample reads TX power from controller and includes it into advertising packet
+CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y