ASoC: omap-mcbsp: Use different method for DMA request when booted with DT

The DMA resource no longer available via this API when booting with DT.
When the board is booted with DT do not use platform_get_resource_byname(),
instead set the dma_data.filter_data to the name of the DMA channel and omap-pcm
can use this name to request the DMA channel.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>