ASoC: samsung: i2s: Move registers cache to common driver data structure

ASoC: samsung: i2s: Move registers cache to common driver data structure

There is no need to keep the PM suspend/resume register cache separate
for each DAI as those registers are common, move related i2s_dai data
structure to the driver's common data structure.  This will allow us
to simplify the code a little eventually and to make it easier to follow.

Change-Id: I91919c337611dc69983d2ee346e988f2e93d0695
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>