[nrf noup] boot: zephyr: Add NCS boot banner

Adds a boot banner which shows as MCUboot

Signed-off-by: Jamie McCrae <[email protected]>
(cherry picked from commit 0148f96)

Author: nordicjm

boot/zephyr/prj.conf

@@ -37,3 +37,6 @@ CONFIG_CBPRINTF_NANO=y
 ### Use the minimal C library to reduce flash usage
 CONFIG_MINIMAL_LIBC=y
 CONFIG_NRF_RTC_TIMER_USER_CHAN_COUNT=0
+
+# NCS boot banner
+CONFIG_NCS_APPLICATION_BOOT_BANNER_STRING="MCUboot"