atomisp/css: Remove PC_MONITORING thread before release

atomisp/css: Remove PC_MONITORING thread before release

BZ: 23514

In case when the atomisp driver is built as module with the PC_MONITORING
turned on, the release of the module will wait for the pc_monitoring thread
which never stops.

This patch stops the thread correctly during release procedure.

Change-Id: I8926a524b94e552d412c764c6746df786f0394ce
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-on: http://android.intel.com:8080/34931
Reviewed-by: Shevchenko, Andriy <andriy.shevchenko@intel.com>
Reviewed-by: Kruger, Jozef <jozef.kruger@intel.com>
Reviewed-by: Wang, Wen W <wen.w.wang@intel.com>
Reviewed-by: Koski, Anttu <anttu.koski@intel.com>
Tested-by: Koski, Anttu <anttu.koski@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>