ASoC: omap-mcbsp: Use the common interrupt line if supported by the SoC

With the common irq the driver only needs to use one interrupt line, and
it provides better debugging possibilites compared to the legacy TX/RX
interrupt lines.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@ti.com>