[nrf noup] board: nordic: thingy53: Default to update only MCUboot type

Changes the default MCUboot mode to update only for the thingy53,
to align with previous bootloader builds

Changes the thingy53 default configuration for sysbuild to enable
using all RAM in the MCUboot image

Signed-off-by: Jamie McCrae <[email protected]>
(cherry picked from commit a06f958)

Author: nordicjm

boards/nordic/thingy53/Kconfig.sysbuild

@@ -7,6 +7,10 @@ choice BOOTLOADER
 	default BOOTLOADER_MCUBOOT
 endchoice
 
+choice MCUBOOT_MODE
+	default MCUBOOT_MODE_OVERWRITE_ONLY
+endchoice
+
 config SECURE_BOOT_NETCORE
 	default y
 
@@ -16,6 +20,9 @@ config NETCORE_APP_UPDATE
 config NRF_DEFAULT_EMPTY
 	default y if SECURE_BOOT_NETCORE
 
+config MCUBOOT_USE_ALL_AVAILABLE_RAM
+	default y if BOARD_THINGY53_NRF5340_CPUAPP_NS && BOOTLOADER_MCUBOOT
+
 endif # BOARD_THINGY53_NRF5340_CPUAPP || BOARD_THINGY53_NRF5340_CPUAPP_NS
 
 config PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY