boot: zephyr: fix compilation with CONFIG_LOG_MINIMAL=y
boot: zephyr: fix compilation with CONFIG_LOG_MINIMAL=y

Fix compilation with CONFIG_LOG_MINIMAL enabled by disabling the
custom log handling code.

Fixes e75e33d9817fefb8ec37b5979f93e3dd41e81b8f

Signed-off-by: Henrik Brix Andersen <24a3f13c22635bab658e39fc5f1e63c575328aae@vestas.com>

utzig/mcuboot,utzig/mcuboot,utzig/mcuboot,ATmobica/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,utzig/mcuboot,ATmobica/mcuboot,ATmobica/mcuboot,utzig/mcuboot,runtimeco/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,runtimeco/mcuboot