Add a predicate that returns if PCIe PTM (Precision Time Measurement)
is enabled.

It will only return true if it's enabled in all the ports in the path
from the device to the root.
Signed-off-by: NVinicius Costa Gomes <vinicius.gomes@intel.com>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>