ASoC: Ux500: Fixup use of clocks

Make sure clocks are being prepared and unprepared as well
as enabled and disabled.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>