PCI/PM: Wrap long lines in documentation

Documentation/power/pci.rst is wrapped to fit in 80 columns, but directory
structure changes made a few lines longer.  Wrap them so they all fit in 80
columns again.

Link: https://lore.kernel.org/r/20191014230016.240912-7-helgaas@kernel.org


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>