zephyr: Restore default log level of info

The default log level has changed to "default", restore it back
to info.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
diff --git a/boot/zephyr/prj.conf b/boot/zephyr/prj.conf
index e4c0129..b6a62a9 100644
--- a/boot/zephyr/prj.conf
+++ b/boot/zephyr/prj.conf
@@ -32,5 +32,7 @@
 CONFIG_LOG_MODE_MINIMAL=y # former CONFIG_MODE_MINIMAL
 ### Ensure Zephyr logging changes don't use more resources
 CONFIG_LOG_DEFAULT_LEVEL=0
+### Use info log level by default
+CONFIG_MCUBOOT_LOG_LEVEL_INF=y
 ### Decrease footprint by ~4 KB in comparison to CBPRINTF_COMPLETE=y
 CONFIG_CBPRINTF_NANO=y