drm/nouveau: Use connector kdev as aux device parent

Set the connector's kernel device as the parent for the aux kernel
device. This allows udev rules to access connector attributes when
creating symlinks to aux devices.

Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190723232808.28128-4-sunpeng.li@amd.com