platform/x86: intel_scu_ipc: Drop intel_scu_ipc_io[read|write][8|16]()

There are no users for these so we can remove them.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>