Revert "ozone/drm: No CTM on external monitor on i915"

This reverts commit d3408523.

Reason for revert: A proper fix landed with https://crrev.com/c/1141356

Original change's description:
> ozone/drm: No CTM on external monitor on i915
> 
> When using a CTM on i915 with some monitors, for some resolutions,
> colors don't look right.
> 
> This CL pretends external displays don't support HW CTM on i915.
> 
> Bug: 848540
> Change-Id: Ibdf3d2ef4bc8e2fce5669086043d54f715263fab
> Reviewed-on: https://chromium-review.googlesource.com/1128406
> Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
> Commit-Queue: Daniele Castagna <dcastagna@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#573140}

TBR=marcheu@chromium.org,dcastagna@chromium.org,afakhry@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 848540
Change-Id: I9a0ae39f46e629879f45f1d43e65a2e43da62505
Reviewed-on: https://chromium-review.googlesource.com/1146782Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Daniele Castagna <dcastagna@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577207}

ui/ozone/platform/drm/common/drm_util.cc

@@ -422,17 +422,9 @@ std::unique_ptr<display::DisplaySnapshot> CreateDisplaySnapshot(
   const display::DisplayConnectionType type = GetDisplayType(info->connector());
   const bool is_aspect_preserving_scaling =
       IsAspectPreserving(fd, info->connector());
-  bool has_color_correction_matrix =
+  const bool has_color_correction_matrix =
       HasColorCorrectionMatrix(fd, info->crtc()) ||
       HasPerPlaneColorCorrectionMatrix(fd, info->crtc());
-  // On i915, some external monitors seem to have washed out colors when a CTM
-  // is set (even if it's the identity) for some resolutions. Claim external
-  // monitors don't support CTM.
-  if (IsDrmModuleName(fd, "i915") &&
-      type != display::DISPLAY_CONNECTION_TYPE_INTERNAL) {
-    has_color_correction_matrix = false;
-  }
-
   // On rk3399 we can set a color correction matrix that will be applied in
   // linear space. https://crbug.com/839020 to track if it will be possible to
   // disable the per-plane degamma/gamma.