ASoC: samsung: i2s: Move SFR pointer to common driver data structure

The SFR region is common for both DAIs so move related data structure
field from struct i2s_dai to the common driver data structure.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>