Replace debug logging code with tracing.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20200123052540.6132-2-linux@roeck-us.net
[PMM: tweak dmald/dmast trace events to fix OSX-only
 format string complaint]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>