ASoC: Change Samsung Kconfig from ASOC_ to SND_SOC_

The rest of ASoC is using SND_SOC_ as the prefix for all the Kconfig
symbols so do so for the new Samsung drivers too, rather than using
ASOC_ as they currently are.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Seungwhan Youn <sw.youn@samsung.com>
Acked-by: Jassi Brar <jassi.brar@samsung.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>