ASoC: Fix i.MX audio build for i.MX3x

Don't unconditionally include the i.MX2x DMA driver, the arch/arm
functions it uses aren't available for i.MX3x.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: NJavier Martin <javier.martin@vista-silicon.com>

sound/soc/imx/Makefile

 # i.MX Platform Support
-snd-soc-imx-objs := imx-ssi.o imx-pcm-fiq.o imx-pcm-dma-mx2.o
+snd-soc-imx-objs := imx-ssi.o imx-pcm-fiq.o
 
 ifdef CONFIG_MACH_MX27
 snd-soc-imx-objs += imx-pcm-dma-mx2.o