Reduce time spent on periodic 1-second traces by constructing the
trace manually, instead of using a printf() format.  This saves 10 ms
in the 1-second event (even if I2C console is not enabled), which is a
significant amount of the allowed 1-second event time.

printf_fast() was considered but rejected, it is affected by the DA A
but on this CPU, which decimal output of values ~2000-9000 (prints
1000-8000, specifically tested 2038, 3038, etc., probably breaks other
values too).

Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>