drm/nvc0/fence: restore pre-suspend fence buffer context on resume

commit d6ba6d21 upstream.

Fixes some unfortunate races on resume.  The G84 version of the code doesn't
need this as "gpuobj"s are automagically suspended/resumed by the core code
whereas pinned buffer objects are not.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>