boot: zephyr: ensure LOG_LEVEL resource savings

Let's ensure that random Zephyr changes in logging don't affect
the resource usage in MCUBOOT, by setting LOG_LEVEL_DEFAULT
to 0.

Signed-off-by: Michael Scott <[email protected]>
Signed-off-by: Andrzej Puzdrowski <[email protected]>

Author: mike-scott

boot/zephyr/prj.conf

@@ -38,3 +38,6 @@ CONFIG_MULTITHREADING=n
 # CONFIG_BT is not set
 # CONFIG_BT_CTLR is not set
 # CONFIG_I2C is not set
+
+### Ensure Zephyr logging changes don't use more resources
+CONFIG_LOG_DEFAULT_LEVEL=0