boot: zephyr: Add optional MCUboot boot banner

Adds an optional MCUboot boot banner which displays the MCUboot
version and zephyr version

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index 1fd9bfc..effedfb 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -700,6 +700,23 @@
 	  increases protection against data leakage from MCUboot to applications via
 	  these caches.
 
+config MCUBOOT_BOOT_BANNER
+	bool "Use MCUboot boot banner"
+	depends on BOOT_BANNER
+	depends on "$(APP_VERSION_EXTENDED_STRING)" != ""
+	default y
+	help
+	  Uses a MCUboot boot banner instead of the default zephyr one, which will output the
+	  MCUboot name and version, followed by the zephyr name and version.
+
+	  For example:
+
+	    *** Booting MCUboot v2.0.0-72-g8c0e36c88663 ***
+	    *** Using Zephyr OS build v3.6.0-2607-gd0be2010c31f ***
+
+config BOOT_BANNER_STRING
+        default "Using Zephyr OS build" if MCUBOOT_BOOT_BANNER
+
 endmenu
 
 config MCUBOOT_DEVICE_SETTINGS