PCI: pciehp: Refer to "Indicators" instead of "LEDs" in comments

The PCIe spec doesn't mention "green LEDs" or "amber LEDs".  Replace those
terms with "Power Indicator" and "Attention Indicator" so the comments
match the spec language.  Comment changes only.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>