boot: zephyr: nrf7120: derive image sectors automatically and enable LTO

nRF7120 builds without Partition Manager, where BOOT_MAX_IMG_SECTORS_AUTO
is enabled by default and derives the sector count from the DTS slot size
and the MRAM erase-block.

Enable link-time optimization (CONFIG_LTO and
CONFIG_ISR_TABLES_LOCAL_DECLARATION) to reduce the MCUboot footprint.

Signed-off-by: Erdem Simsek <erdem.simsek@nordicsemi.no>

Author: erdemsimsek

boot/zephyr/socs/nrf7120_cpuapp.conf

@@ -2,12 +2,13 @@
 #
 # 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
 
-# TODO: below are not yet supported and need fixing
-CONFIG_FPROTECT=n
-
 CONFIG_BOOT_WATCHDOG_FEED=n
+
+# Link Time Optimizations
+CONFIG_ISR_TABLES_LOCAL_DECLARATION=y
+CONFIG_LTO=y