MLK-18680-1: drm: imx: dcss: low latency tracing mechanism

MLK-18680-1: drm: imx: dcss: low latency tracing mechanism

This patch adds a DCSS tracing mechanism that introduces as low latency
as possible, so that it does not affect timings. Instead of text, 64 bit
tags will be logged, together with the system time in nanoseconds. Based
on these, post-processing can be done on any PC to compute deltas,
delays, missed buffers, etc.

Example usage:

echo 1 > /sys/module/imx_dcss_core/parameters/tracing
gplay-1.0 movie.mpg
echo 0 > /sys/module/imx_dcss_core/parameters/tracing

To dump the trace:
cat /sys/kernel/debug/imx-dcss/dump_trace_log > trace.txt

With the help of a scripting language (awk), the trace can then be
post-processed and analyzed on the PC.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>