drm/amd/display: Add log end specifier

[Why]
Some debug tools, sometimes wrap around to multiple lines which causes
issues with the DPM test script while it is looking for the logs. Need a
way to tell when the log is finished.

[How]
Added "LOG_END" to the end of the log.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Relja Vojvodic <relja.vojvodic@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>