drm/i915: Init HSW watermark tracking in intel_modeset_setup_hw_state()

Fill out the HSW watermark s/w tracking structures with the current
hardware state in intel_modeset_setup_hw_state(). This allows us to skip
the HW state readback during watermark programming and just use the values
we keep around in dev_priv->wm. Reduces the overhead of the watermark
programming quite a bit.

v2: s/init_wm/wm_get_hw_state
    Remove stale comment about sprites
    Make DDB partitioning readout safer

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: Fix whitespace fail.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e6a4ca1..53ad5cb 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10839,6 +10839,9 @@
 		pll->on = false;
 	}
 
+	if (IS_HASWELL(dev))
+		ilk_wm_get_hw_state(dev);
+
 	if (force_restore) {
 		i915_redisable_vga(dev);