The wm9712/wm9713 has separate mixers for the left and the right channel,
but the inputs to the mixers are enabled/disabled by the same control.
Currently this is implemented by the driver by registering two virtual
controls for each physical control, one for the left mixer and one for the
right mixer.

Using virtual registers will no longer work when the driver has
been converted to regmap. This patch converts the driver to use controls
with custom put/get callbacks instead which implement the logic making sure
that the physical control is unmuted when either the left or the right
control is unmuted.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NMark Brown <broonie@kernel.org>