Revert "drm/i915: Track active streams also for DP SST"

Revert "drm/i915: Track active streams also for DP SST"

This reverts commit dc1285df25181574ea2ff28a9445bf02ce2132b7.

active_streams will get totally out of whack with SST unless we
sync up with the hw state at readout, obviously! We don't yet
do that, so now the WARNs fire all the time. Let's revert :(

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470413142-26402-1-git-send-email-ville.syrjala@linux.intel.com
References: https://bugs.freedesktop.org/show_bug.cgi?id=95472#c14
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>