ACPI / PMIC: Add opregion driver for Intel BXT WhiskeyCove PMIC

This patch adds operation region driver for Intel BXT WhiskeyCove
PMIC. The register mapping is done as per the BXT WC data sheet.

Signed-off-by: Ajay Thomas <ajay.thomas.david.rajamanickam@intel.com>
Signed-off-by: Bin Gao <bin.gao@intel.com>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>