MLK-12464-1: ASoC: fsl: imx-wm8960: Fix no clock after suspend/resume randomly

MLK-12464-1: ASoC: fsl: imx-wm8960: Fix no clock after suspend/resume randomly

After suspend and resume, the wm8960 codec will change the state from
BIAS_OFF to BIAS_ON, in this time, the hw_free is called, the PLL will be
diabled, and next instance is started in rapid sequence, hw_params is called
But PLL is not enabled, because the bias state is not BIAS_ON.

As PLL is disabled in BIAS_ON->BIAS_STANDBY, so don't need to disable pll
in hw_free of machine driver.

Signed-off-by: Shengjiu Wang <shengjiu.wang@freescale.com>