PCI/ACPI: Optimize device state transition delays

The PCI "ACPI additions for FW latency optimizations" ECN (link below)
defines two functions in the PCI _DSM:

  Function 8, "Reset Delay," applies to the entire hierarchy below a PCI
  host bridge.  If it returns one, the OS may assume that all devices in
  the hierarchy have already completed power-on reset delays.

  Function 9, "Device Readiness Durations," applies only to the object
  where it is located.  It returns delay durations required after various
  events if the device requires less time than the spec requires.  Delays
  from this function take precedence over the Reset Delay function.

Add support for Reset Delay and part of Device Readiness Durations.

[bhelgaas: changelog, comments]
Link: https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>