drm/i915/perf: Reintroduce wait on OA configuration completion

commit 08f56f8f upstream.

We still need to wait for the initial OA configuration to happen
before we enable OA report writes to the OA buffer.

Reported-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 15d0ace1 ("drm/i915/perf: execute OA configuration from command stream")
Closes: https://gitlab.freedesktop.org/drm/intel/issues/1356


Testcase: igt/perf/stream-open-close
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200302085812.4172450-7-chris@chris-wilson.co.uk


(cherry picked from commit 4b4e973d)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>