ASoC: Samsung: Set default rclk source rate

Since the rclk_srcrate is cleared upon startup, it should be
initialized upon second and later 'open' calls to the device
with same root-clock source. The bug is otherwise visible in
Codec-Slave mode.

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>