drm/i915: Add pipe enable/disable tracepoints

Add tracepoints for pipe enable/disable. We'll include the
frame/scanline counters for all pipes in these tracepoints to
help in diagnosing underruns and whatnot when enabling/disabling
pipes in parallel with plane updates/flips on another pipe.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190206204910.13965-2-ville.syrjala@linux.intel.com


Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>