drm/i915: Fix wrong CDCLK adjustment changes

Previous patch didn't take into account all pipes
but only those in state, which could cause wrong
CDCLK conclcusions and calculations.
Also there was a severe issue with min_cdclk being
assigned to 0 every compare cycle.

Too bad this was found by me only after merge.
This could be also causing the issues in test, however
not clear - anyway marking this as fixing the
"Adjust CDCLK accordingly to our DBuf bw needs".

v2: - s/pipe/crtc->pipe/
    - save a bit of instructions by
      skipping inactive pipes, without
      getting 0 DBuf slice mask for it.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Fixes: cd191546 ("drm/i915: Adjust CDCLK accordingly to our DBuf bw needs")
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200601173058.5084-1-stanislav.lisovskiy@intel.com