CHERRY-PICK: CHROMIUM: drm/i915: Treat cursor plane as another sprite plane for BSW

Work around the pipe C FIFO underruns that cause display failure by
enabling sprite plane for cursor.

Note: This patch for BSW is based on Maarten Lankhorst's work that
enables universal plane support.

BUG=chrome-os-partner:48532
TEST=Verify there are no graphics artifacts.
TEST=Verify that moving the cursor swiftly between the primary and
extended screens does not cause display failures.

Original-Change-Id: Icf48036e3578dd39ef885bab190a10382384b5a6
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Kalyan Kondapally <kalyan.kondapally@intel.com>
Signed-off-by: Pandiyan Dhinakaran <dhinakaran.pandiyan@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/326925
Commit-Ready: Wayne Boyer <wayne.boyer@intel.com>
Tested-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Tested-by: Brian J Lovin <brian.j.lovin@intel.com>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>

Conflicts:

	drivers/gpu/drm/i915/intel_sprite.c

Change-Id: Ic68533624ca6f16d3a970ddb46cf53fbf7356c0f
Reviewed-on: https://chromium-review.googlesource.com/329786
Tested-by: Anson Tseng <anson.tseng@intel.com>
Reviewed-by: Josafat Garcia <josafat@chromium.org>
Commit-Queue: Anson Tseng <anson.tseng@intel.com>
4 files changed