[nrf noup] boot/zephyr/boards: nRF54l15pdk ext flash cfg

Added configuration which allows to build MCUboot for
nrf54l15pdk_nrf54l15_cpuapp with external flash used for
the secondary slot.

Signed-off-by: Andrzej Puzdrowski <[email protected]>
(cherry picked from commit 78bc87c)

Author: nvlsianpu

boot/zephyr/boards/nrf54l15pdk_nrf54l15_cpuapp_ext_flash.conf

@@ -0,0 +1,8 @@
+CONFIG_MULTITHREADING=y
+CONFIG_SPI=y
+CONFIG_SPI_NOR=y
+CONFIG_FLASH=y
+CONFIG_PM_PARTITION_SIZE_MCUBOOT=0x14000
+CONFIG_MAIN_STACK_SIZE=20480
+CONFIG_BOOT_MAX_IMG_SECTORS=512
+CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096

boot/zephyr/boards/nrf54l15pdk_nrf54l15_cpuapp_ext_flash.overlay

@@ -0,0 +1,10 @@
+/ {
+	chosen {
+		nordic,pm-ext-flash = &mx25r64;
+	};
+};
+
+
+&mx25r64 {
+	status = "okay";
+};