ASoC: Samsung: Rename s3c64xx I2S device

Since the I2S of S3C64XX and newer SoCs are incremental
versions of each other with changes managable in a single
driver, rename the 's3c64xx-iis' -> 'samsung-i2s'

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