drm/i915: Fix SKL+ watermarks for 90/270 rotation

drm/i915: Fix SKL+ watermarks for 90/270 rotation

skl_check_plane_surface() already rotates the clipped plane source
coordinates to match the scanout direction because that's the way
the GTT mapping is set up. Thus we no longer need to rotate the
coordinates in the watermark code.

For cursors we use the non-clipped coordinates which are not rotated
appropriately, but that doesn't actually matter since cursors don't
even support 90/270 degree rotation.

v2: Resolve conflicts from SKL+ wm rework

Cc: stable@vger.kernel.org
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: b63a16f6cd89 ("drm/i915: Compute display surface offset in the plane check hook for SKL+")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170331180056.14086-3-ville.syrjala@linux.intel.com
Tested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>