ASoC: ti: davinci-mcasp: Handle missing required DT properties

ASoC: ti: davinci-mcasp: Handle missing required DT properties

McASP needs three required properties to be usable for audio:
op-mode, tdm-slots and the serial-dir array.

Instead of probing the driver even without the needed information we should
make sure that all the parameters are provided for operation.

The fact that McASP can act as a GPIO controller for it's pins complicates
this a bit, but as a general rule we can:
- we fail the probe if McASP is not configured to be used as gpiochip
- we will not register the DAI (and PCM) if gpiochip is defined

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20201106072551.689-5-peter.ujfalusi@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>