PCI/PM: Drop the runtime_d3cold device flag

The runtime_d3cold flag is not needed any more, so drop it.

Link: https://lore.kernel.org/r/8077784.T7Z3S40VBb@kreacher


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