ASoC: wm8994: Add support for setting MCLK clock rate

ASoC: wm8994: Add support for setting MCLK clock rate

Extend the set_sysclk() handler so we also set frequency of the MCLK1,
MCLK2 clocks through clk API when those clocks are specified in DT.

Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20190920130218.32690-4-s.nawrocki@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org>