samples: matter: Enable LTO for all nRF7002 DK variants.

We need to use Link Time Optimization to fit the code into the
FLASH memory space.

Signed-off-by: Arkadiusz Balys <arkadiusz.balys@nordicsemi.no>

samples/matter/lock/boards/nrf7002dk_nrf5340_cpuapp.conf

@@ -0,0 +1,9 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+# Enable LTO to decrease the flash usage.
+CONFIG_LTO=y
+CONFIG_ISR_TABLES_LOCAL_DECLARATION=y