ASoC: fsl: mpc5200_dma: remove unused psc_dma

linux/sound/soc/fsl/mpc5200_dma.c:305:18: warning: unused variable \
	psc_dma’ [-Wunused-variable]

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>