platform/x86: intel_scu_ipc: Drop intel_scu_ipc_i2c_cntrl()

There are no existing users for this functionality so drop it from the
driver completely. This also means we don't need to keep the struct
intel_scu_ipc_pdata_t around anymore so remove that as well.

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>