disp: msm: sde: remove unused output parameter in _get_tearcheck_threshold

Remove the output parameter "extra_frame_trigger_time" from this
function as callers are not using it, so it is not needed.

Change-Id: I98fcfe974c64da9ce62456a693330b898707e6b4
Signed-off-by: Steve Cohen <cohens@codeaurora.org>