ASoC: atmel: Revert previous fix for Kconfig limations

After discussing with the Kconfig maintainer, we found a better fiw
allowing to keep each driver as modules.

This reverts commit 0ef9dc13.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/atmel/Kconfig

@@ -9,10 +9,10 @@ config SND_ATMEL_SOC
 if SND_ATMEL_SOC
 
 config SND_ATMEL_SOC_PDC
-	bool
+	tristate
 
 config SND_ATMEL_SOC_DMA
-	bool
+	tristate
 	select SND_SOC_GENERIC_DMAENGINE_PCM
 
 config SND_ATMEL_SOC_SSC

sound/soc/atmel/Makefile

 # AT91 Platform Support
-snd-soc-atmel-pcm-$(CONFIG_SND_ATMEL_SOC_PDC) := atmel-pcm-pdc.o
-snd-soc-atmel-pcm-$(CONFIG_SND_ATMEL_SOC_DMA) += atmel-pcm-dma.o
-snd-soc-atmel_ssc_dai-objs := atmel_ssc_dai.o $(snd-soc-atmel-pcm-y)
+snd-soc-atmel-pcm-pdc-objs := atmel-pcm-pdc.o
+snd-soc-atmel-pcm-dma-objs := atmel-pcm-dma.o
+snd-soc-atmel_ssc_dai-objs := atmel_ssc_dai.o
 
+obj-$(CONFIG_SND_ATMEL_SOC_PDC) += snd-soc-atmel-pcm-pdc.o
+obj-$(CONFIG_SND_ATMEL_SOC_DMA) += snd-soc-atmel-pcm-dma.o
 obj-$(CONFIG_SND_ATMEL_SOC_SSC) += snd-soc-atmel_ssc_dai.o
 
 # AT91 Machine Support