ASoC: pcm3168a: Add support for optional RST gpio handling

In case the RST line is connected to a GPIO line it needs to be pulled high
when the driver probes to be able to use the codec.

Add support also for cases when more than one codec is is controlled by the
same GPIO line by requesting the gpio with GPIOD_FLAGS_BIT_NONEXCLUSIVE.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>

Link: https://lore.kernel.org/r/20191113124734.27984-3-peter.ujfalusi@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>