ASoC: ops: Fix stereo change notifications in snd_soc_put_xr_sx()

When writing out a stereo control we discard the change notification from
the first channel, meaning that events are only generated based on changes
to the second channel. Ensure that we report a change if either channel
has changed.

Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org