drm/i915: Add plane update/disable tracepoints

Add tracepoints for plane programming. The tracepoints will dump
the frame and scanline counters, so this can be used to verify eg. that
the plane gets reprogrammed at the right time with respect to watermark
programming (if we have appropriate tracepoints for that as well).

v2: Rebase due to legacy cursor changes

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170302171508.1666-16-ville.syrjala@linux.intel.com