Add Texas Instruments's PCM1789 DAC support.
It is a simple DAC and does not have many registers.

One particularity about this DAC is that the clocks must be
always enabled. Also, an entire software reset is necessary
while starting to play a sound otherwise, the clocks are not
synchronized (so the DAC is not able to send data).
Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>