rtos: do not use LOG_OUTPUT

LOG_OUTPUT is not intended for general output so use the correct LOG_*
functions instead.

Change-Id: I48d0fe765637024dbafc68f2ea08219d3ff42754
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1104
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>