Add documentation for two attributes, status and hrv, in
Documentation/ABI/testing/sysfs-bus-acpi.

Compiled from git logs and the ACPI specification.
Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
[ rjw: Minor changes ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>