ASoC: samsung: Fix clock handling in S3C24XX_UDA134X card

There is no "pclk" alias in the s3c2440 clk driver for "soc-audio"
device so related clk_get() fails, which prevents any operation
of the S3C24XX_UDA134X sound card.
Instead we get the clock on behalf of the I2S device, i.e. we use
the I2S block gate clock which has PCLK is its parent clock.

Without this patch there is an error like:

s3c24xx_uda134x_startup cannot get pclk
ASoC: UDA134X startup failed: -2

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