Support PMIC operation region for CrystalCove and XPower

v3:
Only some function/variable name changes, no functiona changes:
- Replace the dptf/DPTF word originate from the BIOS ACPI table with more meaningful word thermal/THERMAL in all places;
- Eliminate the soc part in various structure and function names to make them shorter:
intel_soc_pmic_opregion -> intel_pmic_opregion intel_soc_pmic_pmop_handler -> intel_pmic_pmop_handler intel_soc_pmic_install_opregion_handler -> intel_pmic_install_opregion_handler etc.

v2:
Place PMIC operation files under drivers/acpi/pmic instead of drivers/acpi/pmic_opregion as suggested by Rafael;
Rename PMIC operation files to make them shorter as suggested by Rafael.

v1:
On Intel Baytrail-T and Baytrail-T-CR platforms, there are two customized ACPI operation regions defined for the Power Management Integrated Circuit device, one is for power resource handling and one is for thermal: sensor temperature reporting, trip point setting, etc. There are different PMIC chips used on those platforms and though each has the same two operation regions and functionality, their implementation is different so every PMIC will need a driver. But since their functionality is similar, some common code is abstracted into the intel_soc_pmic_opregion.c.

The last version is posted here:
https://lkml.org/lkml/2014/9/8/801

Changes since then:
1 Move to drivers/acpi as discussed on the above thread;
2 Added support for XPower AXP288 PMIC operation region support; 3 Since operation region handler can not be removed(at the moment at least),
use bool for the two operation region driver configs instead of tristate; Another reason to do this is that, with Mika's MFD ACPI support patch, all those MFD cell devices created will have the same modalias as their parent's so it doesn't make much sense to compile these drivers into modules.

Patch 1 applies on top of Rafael's pm-next branch, and then patch 2 and patch 3 needs merge of Lee's mfd/ib-mfd-iio-3.19 branch where the PMIC driver XPower AXP288 and iio driver axp288_adc is located.

Aaron Lu (3):
ACPI / PMIC: support PMIC operation region for CrystalCove ACPI / PMIC: support PMIC operation region for XPower AXP288 ACPI / PMIC: AXP288: support virtual GPIO in ACPI table