[ALSA] soc - fix S3C2410 i2s programming error

S3C2410 i2s driver currently manages only i2s protocol (and not left
justified one) and slave mode.
With this small patch, other modes are possible.

Signed-off-by: Davide Rizzo <davide@elpa.it>
Acked-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>