drm: i915: Wait for fences on new fb, not old

drm: i915: Wait for fences on new fb, not old

The previous code would wait for fences on the framebuffer from the old
plane state to complete, rather than the new, so you would see tearing
everywhere. Fix this to wait on the new state before we make it active.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Fixes: 94f050246b42 ("drm/i915: nonblocking commit")
Cc: stable@vger.kernel.org
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161021144454.6288-1-daniels@collabora.com
(cherry picked from commit 2d2c5ad83f772d7d7b0bb8348ecea42e88f89ab0)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>