ASoC: dmic: Fix clock parenting

In 4.16 the clock hierarchy got changed by
a5c82a09 ARM: dts: omap4: add clkctrl nodes

The fck of dmic is no longer a mux clock, it's parent is.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org # 4.16+