drm/nouveau: wait for the exclusive fence after the shared ones v2

drm/nouveau: wait for the exclusive fence after the shared ones v2

commit 67f74302f45d5d862f22ced3297624e50ac352f0 upstream.

Always waiting for the exclusive fence resulted on some performance
regressions. So try to wait for the shared fences first, then the
exclusive fence should always be signaled already.

v2: fix incorrectly placed "(", add some comment why we do this.

Signed-off-by: Christian König <christian.koenig@amd.com>
Tested-by: Stefan Fritsch <sf@sfritsch.de>
Tested-by: Dan Moulding <dmoulding@me.com>
Acked-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Cc: <stable@vger.kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211209102335.18321-1-christian.koenig@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>