ASoC: samsung: i2s: Fix prescaler setting for the secondary DAI

Make sure i2s->rclk_srcrate is properly initialized also during
playback through the secondary DAI.

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