platform/x86: Add Elkhart Lake SCU/PMC support

Intel Elkhart Lake exposes SCU/PMC as an ACPI device that only supports
IPC functionality so add a platform driver supporting it. Interrupt is
optional so we let intel_scu_ipc_probe() to decide based on the passed
platform data whether it uses interrupt or polling.

Co-developed-by: Divya Sasidharan <divya.s.sasidharan@intel.com>
Signed-off-by: Divya Sasidharan <divya.s.sasidharan@intel.com>
Co-developed-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>