Add per platform mcuboot_logging.h files

New logging macros were added for all supported platforms, following the
documentation defined in the template config file.

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index 87664ec..10eb22d 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -78,6 +78,15 @@
 
 	  This is not available for all targets.
 
+config BOOT_HAVE_LOGGING
+	bool "MCUboot have logging enabled"
+	default y
+	select SYS_LOG
+	help
+	  If y, enables logging on the serial port. The log level can
+	  be defined by setting `SYS_LOG_DEFAULT_LEVEL`.
+	  If unsure, leave at the default value.
+
 menuconfig MCUBOOT_SERIAL
 	bool "MCUboot serial recovery"
 	default n