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/CMakeLists.txt b/boot/zephyr/CMakeLists.txt
index f6c4b7e..45548e0 100644
--- a/boot/zephyr/CMakeLists.txt
+++ b/boot/zephyr/CMakeLists.txt
@@ -358,6 +358,11 @@
 )
 endif()
 
+if(CONFIG_MCUBOOT_BOOT_BANNER)
+  # Replace Zephyr's boot banner with the MCUboot one
+  zephyr_sources(kernel/banner.c)
+endif()
+
 if(SYSBUILD)
   function(align_up num align result)
     math(EXPR out "(((${num}) + ((${align}) - 1)) & ~((${align}) - 1))")