platform/x86: intel_skl_int3472: Provide skl_int3472_unregister_clock()

For the sake of APIs to be properly layered provide
skl_int3472_unregister_clock().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Daniel Scally <djrscally@gmail.com>
Tested-by: Daniel Scally <djrscally@gmail.com>
Link: https://lore.kernel.org/r/20210618125516.53510-6-andriy.shevchenko@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>