ASoC: Fix recursive dependency due to select ATMEL_SSC in SND_ATMEL_SOC_SSC

commit 739be96a "ASoC: Fix build dependency for SND_ATMEL_SOC_SSC"
introduces below build warnings:

drivers/misc/Kconfig:212:error: recursive dependency detected!
drivers/misc/Kconfig:212:       symbol ATMEL_SSC is selected by SND_ATMEL_SOC_SSC
sound/soc/atmel/Kconfig:9:      symbol SND_ATMEL_SOC_SSC is selected by SND_AT91_SOC_SAM9G20_WM8731
sound/soc/atmel/Kconfig:18:     symbol SND_AT91_SOC_SAM9G20_WM8731 depends on ATMEL_SSC

SND_ATMEL_SOC_SSC needs ATMEL_SSC to pass compilation.
This patch remove the "select ATMEL_SSC" from SND_ATMEL_SOC_SSC to avoid above
warnings. And then ensures all the machine drivers that select SND_ATMEL_SOC_SSC
need to depend on ATMEL_SSC.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>