drm/i915: Partial revert of atomic watermark series

drm/i915: Partial revert of atomic watermark series

It's been reported that the atomic watermark series triggers some
regressions on SKL, which we haven't been able to track down yet.  Let's
temporarily revert these patches while we track down the root cause.

This commit squashes the reverts of:
  5ac064f drm/i915: Calculate watermark configuration during atomic check (v2)
  177f95f drm/i915: Don't set plane visible during HW readout if CRTC is off
  b7d1161 drm/i915: Calculate ILK-style watermarks during atomic check (v3)
  17019e1 drm/i915: Calculate pipe watermarks into CRTC state (v3)
  7cace4b drm/i915: Refactor ilk_update_wm (v3)

Reference: http://lists.freedesktop.org/archives/intel-gfx/2015-October/077190.html
Cc: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
Cc: "Vetter, Daniel" <daniel.vetter@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>