ASoC: davinci-mcasp: Correct am33xx snd_platform_data name

An earlier patch overlooked this when the compatible has been changed from
omap2 -> am33x.
Rename omap2_mcasp_pdata to am33xx_mcasp_pdata.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>