x86: power: Add an ACPI PMC uclass

Intel x86 SoCs have a power manager/controller which handles several
power-related aspects of the platform. Add a uclass for this, with a few
useful operations.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
6 files changed