ARM: dts: exynos: Specify I2S assigned clocks in proper node

The assigned parent clocks should be normally specified in the consumer
device's DT node, this ensures respective driver always sees correct clock
settings when required.

This patch fixes regression in audio subsystem on Odroid XU3/XU4 boards
that appeared after commits:

commit 647d04f8 ("ASoC: samsung: i2s: Ensure the RCLK rate is properly determined")
commit 995e73e5 ("ASoC: samsung: i2s: Fix rclk_srcrate handling")
commit 48279c53 ("ASoC: samsung: i2s: Prevent external abort on exynos5433 I2S1 access")

Without this patch the driver gets wrong clock as the I2S function clock
(op_clk) in probe() and effectively the clock which is finally assigned
from DT is not being enabled/disabled in the runtime resume/suspend ops.

Without the above listed commits the EXYNOS_I2S_BUS clock was always set
as parent of CLK_I2S_RCLK_SRC regardless of DT settings so there was no issue
with not enabled EXYNOS_SCLK_I2S.

Cc: <stable@vger.kernel.org> # 4.17.x
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>