ASoC: S3C: I2Sv2: Reject immidiate register value

Towards generalizing CPU driver interface, do not accept direct field
values for the BCLK and RCLK.
The machine driver should simply request the FS-multiple and not provide
the value to be set in divide field of IISMOD.

[Confirmed by Jassi that no existing machine drivers are affected --
broonie]

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>