ACPI: power_meter: remove double kfree()

resource->domain_devices can be double kfree()'d in a couple of places.
Fix this by setting num_domain_devices = 0 after the kfree().

Coverity CID: 13356, 13355, 13354

Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com>
Acked-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Len Brown <len.brown@intel.com>