drm/i915: Put "cooked" vlank counters in frame CRC lines

Use drm_accurate_vblank_count so we have the full 32 bit to represent
the frame counter and userspace has a simpler way of knowing when the
counter wraps around.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Robert Foss <robert.foss@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110134305.26326-3-tomeu.vizoso@collabora.com