ASoC: ti: davinci-mcasp: Use platform_get_irq_byname_optional

ASoC: ti: davinci-mcasp: Use platform_get_irq_byname_optional

Depending on the integration of McASP either the 'common' or the
'rx' and 'tx' or only the 'tx' interrupt number is valid, provided.

By switching to platform_get_irq_byname_optional() we can clean up the
bootlog from messages like:

davinci-mcasp 2ba0000.mcasp: IRQ common not found

The irq number == 0 is not valid, fix the check at the same time.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20201106072551.689-2-peter.ujfalusi@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>