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

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

commit 08f56f8f3799b2ed1c5ac7eed6d86a4926289655 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: 15d0ace1f876 ("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 4b4e973d5eb89244b67d3223b60f752d0479f253)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>