ASoC: Samsung: I2S: Modify driver to give more flexibility

This patch modifies the i2s driver to give flexibility towards register
handling. This is a pre requirement for enabling i2s support on Exynos5420.
This patch modifies only the required registers as a pre-requirement to
support on Exynos5420.

Signed-off-by: Padmavathi Venna <padma.v@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>