ASoC: omap-dmic: Do not use platform_get_resource_byname() for DMA

The DMA resource no longer available via this API when booting with DT.
DMIC is only available on OMAP4/5 and both can boot with DT only.
Set the dma_data.filter_data to the DMA name which will be used by omap-pcm
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>