hwmon driver for ACPI 4.0 power meters

This driver exposes ACPI 4.0 compliant power meters as hardware monitoring
devices.  This second revision of the driver also exports the ACPI string
info as sysfs attributes, a list of the devices that the meter measures,
and will send ACPI notifications over the ACPI netlink socket.  This
latest revision only enables the power capping controls if it can be
confirmed that the power cap can be enforced by the hardware and explains
how the notification interfaces work.

[akpm@linux-foundation.org: remove default-y]
[akpm@linux-foundation.org: build fix]
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>