PCI: pciehp: Remove unused interrupt events

The list of interrupt events (INT_BUTTON_IGNORE, INT_PRESENCE_ON, etc.) was
copied from other hotplug drivers, but pciehp doesn't use them all.

Remove the interrupt events that aren't used by pciehp.

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