ARM: OMAP2+: McBSP: Do not create legacy devices when booting with DT data

Only create the devices in a legacy way if we do not have the DT data.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>