ASoC: atmel: fix build error with CONFIG_SND_ATMEL_SOC_DMA=m

If CONFIG_SND_ATMEL_SOC_DMA=m, build error:

sound/soc/atmel/atmel_ssc_dai.o: In function `atmel_ssc_set_audio':
(.text+0x7cd): undefined reference to `atmel_pcm_dma_platform_register'

Function atmel_pcm_dma_platform_register is defined under
CONFIG SND_ATMEL_SOC_DMA, so select SND_ATMEL_SOC_DMA in
CONFIG SND_ATMEL_SOC_SSC, same to CONFIG_SND_ATMEL_SOC_PDC.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Link: https://lore.kernel.org/r/20200113133242.144550-1-chenzhou10@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/atmel/Kconfig

@@ -19,6 +19,8 @@ config SND_ATMEL_SOC_DMA
 
 config SND_ATMEL_SOC_SSC
 	tristate
+	select SND_ATMEL_SOC_DMA
+	select SND_ATMEL_SOC_PDC
 
 config SND_ATMEL_SOC_SSC_PDC
 	tristate "SoC PCM DAI support for AT91 SSC controller using PDC"