PCI/PM: Revert "PCI/PM: Apply D2 delay as milliseconds, not microseconds"

This reverts commit 7e24bc34.

7e24bc34 was based on PCIe r5.0, sec 5.9, which claims we need a 200 ms
delay when transitioning to or from D2.  However, sec 5.3.1.3 states the
delay as 200 μs (microseconds), as does the table in PCIe r4.0, sec 5.9.1.

This looks like a typo in the r5.0 spec, so revert back to a 200 μs delay
instead of a 200 ms delay.

Fixes: 7e24bc34 ("PCI/PM: Apply D2 delay as milliseconds, not microseconds")
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>