coresight: add stm logging to support optimization in trace printk

The function trace_printk() performs optimization by determining if
there are no format parameters in argument string and calls appropriate
apis to write to ftrace buffer. Add STM logging to support this
optimization in order to allow CoreSight STM tracing for optimized
trace_printk path.

Change-Id: I1a77291e77410c6ed99474335a6d25742c409e47
Signed-off-by: Aparna Das <adas@codeaurora.org>