ASoC: mxs: Depends on COMMON_CLK

The SAIF driver is a clock provider so specifically needs the common
clock implementedation.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>