boot: zephyr: boards: Add nrf54l15dk configuration

Adds the configuration for this board

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

boot/zephyr/boards/nrf54l15dk_nrf54l15_cpuapp.conf

@@ -0,0 +1,10 @@
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+CONFIG_BOOT_MAX_IMG_SECTORS=256
+
+# Ensure that the SPI NOR driver is disabled by default
+CONFIG_SPI_NOR=n
+
+CONFIG_BOOT_WATCHDOG_FEED=n