ASoC: wm_adsp: Fix NULL dereference when removing firmware controls

In the Linux kernel, the following vulnerability has been resolved: ASoC: wm_adsp: Fix NULL dereference when removing firmware controls In wm_adsp_control_remove() check that the priv pointer is not NULL before attempting to cleanup what it points to. When cs_dsp creates a control it calls wm_adsp_control_add_cb() so that wm_adsp can create its own private control data. There are two cases where private data is not created: 1. The control is a SYSTEM control, so an ALSA control is not created. 2. The codec driver has registered a control_add() callback that hides the control, so wm_adsp_control_add() is not called. When cs_dsp_remove destroys its control list it calls wm_adsp_control_remove() for each control. But wm_adsp_control_remove() was attempting to cleanup the private data pointed to by cs_ctl->priv without checking the pointer for NULL.