ASoC: fsl: fix snd-soc-imx-pcm module build

When building modules with CONFIG_SND_IMX_SOC=m in imx_v6_v7_defconfig,
we will see the following link error.

  LD [M]  sound/soc/fsl/snd-soc-fsl-ssi.o
  LD [M]  sound/soc/fsl/snd-soc-fsl-utils.o
  LD [M]  sound/soc/fsl/snd-soc-imx-ssi.o
  LD [M]  sound/soc/fsl/snd-soc-imx-audmux.o
  LD [M]  sound/soc/fsl/snd-soc-imx-pcm.o
sound/soc/fsl/imx-pcm-dma.o: In function `init_module':
imx-pcm-dma.c:(.init.text+0x0): multiple definition of `init_module'
sound/soc/fsl/imx-pcm-fiq.o:imx-pcm-fiq.c:(.init.text+0x0): first defined here
sound/soc/fsl/imx-pcm-dma.o: In function `cleanup_module':
imx-pcm-dma.c:(.exit.text+0x0): multiple definition of `cleanup_module'
sound/soc/fsl/imx-pcm-fiq.o:imx-pcm-fiq.c:(.exit.text+0x0): first defined here
make[4]: *** [sound/soc/fsl/snd-soc-imx-pcm.o] Error 1

The module snd-soc-imx-pcm is designed to link imx-pcm.o with
imx-pcm-dma.o or imx-pcm-fiq.o depending on if option SND_SOC_IMX_PCM_DMA
or SND_SOC_IMX_PCM_FIQ is enabled.  Both imx-pcm-dma and imx-pcm-fiq
register their own module_platform_driver.  However, these two options
are not mutually exclusive and can be enabled together.  And that's
why we see above multiple init_module definition error.

Instead of having both imx-pcm-dma and imx-pcm-fiq register their
own platform_driver, we should do only once in imx-pcm.c.  Using
platform_device_id to distinguish between imx-pcm-dma and imx-pcm-fiq,
we can run-time call imx-pcm-dma/fiq specific initialization in .probe
hook to have module snd-soc-imx-pcm work for both cases.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/fsl/imx-pcm-dma.c b/sound/soc/fsl/imx-pcm-dma.c
index bf363d8..500f8ce 100644
--- a/sound/soc/fsl/imx-pcm-dma.c
+++ b/sound/soc/fsl/imx-pcm-dma.c
@@ -154,26 +154,7 @@
 	.pcm_free	= imx_pcm_free,
 };
 
-static int imx_soc_platform_probe(struct platform_device *pdev)
+int imx_pcm_dma_init(struct platform_device *pdev)
 {
 	return snd_soc_register_platform(&pdev->dev, &imx_soc_platform_mx2);
 }
-
-static int imx_soc_platform_remove(struct platform_device *pdev)
-{
-	snd_soc_unregister_platform(&pdev->dev);
-	return 0;
-}
-
-static struct platform_driver imx_pcm_driver = {
-	.driver = {
-			.name = "imx-pcm-audio",
-			.owner = THIS_MODULE,
-	},
-	.probe = imx_soc_platform_probe,
-	.remove = imx_soc_platform_remove,
-};
-
-module_platform_driver(imx_pcm_driver);
-MODULE_LICENSE("GPL");
-MODULE_ALIAS("platform:imx-pcm-audio");