drm/i915/skl: Eliminate usage of pipe_wm_parameters from SKL-style WM (v4)

Just pull the info out of the state structures rather than staging
it in an additional set of structures.  To make this more
straightforward, we change the signature of several internal WM
functions to take the crtc state as a parameter.

v2:
 - Don't forget to skip cursor planes on a loop in the DDB allocation
   function to match original behavior.  (Ander)
 - Change a use of intel_crtc->active to cstate->active.  They should
   be identical, but it's better to be consistent.  (Ander)
 - Rework more function signatures to pass states rather than crtc for
   consistency. (Ander)

v3:
  - Add missing "+ 1" to skl_wm_plane_id()'s 'overlay' case. (Maarten)
  - Packed formats should pass '0' to drm_format_plane_cpp(), not 1.
    (Maarten)
  - Drop unwanted WARN_ON() for disabled planes when calculating data
    rate for SKL.  (Maarten)

v4:
 - Don't include cursor plane in total relative data rate calculation;
   we've already handled the cursor allocation earlier.
 - Fix 'bytes_per_pixel' calculation braindamage.  Somehow I hardcoded
   the NV12 format as a parameter rather than the actual
   fb->pixel_format, and even then still managed to get the format plane
   wrong.  (Ville)
 - Use plane->state->fb rather than plane->fb in
   skl_allocate_pipe_ddb(); the plane->fb pointer isn't updated until
   after we've done our watermark recalculation, so it has stale
   values.  (Bob Paauwe)
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by(v3): Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Paauwe, Bob J <bob.j.paauwe@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
References: http://lists.freedesktop.org/archives/intel-gfx/2015-September/077060.html
References: http://lists.freedesktop.org/archives/intel-gfx/2015-October/077721.html
Smoke-tested-by(v4): Paulo Zanoni <paulo.r.zanoni@intel.com> (SKL)
Link: http://patchwork.freedesktop.org/patch/61968/