i440fx/acpi: don't hot-unplug cold plugged bridges when their hotplug switch is off

[Ani Sinha]

I have seen that when hotplug for pci bridge devices are turned off and devices 
are attached
behind the bridge, I still see Windows trying to hot remove the pci bridge and 
failing. Today
looking at the AML disassembly, I realized that we are addding slot enumeration 
and EJ0
methods even for the slot where the bridge is attached. 

Please see the video: https://youtu.be/pME2sjyQweo

This does not seem right. A cold-plugged bridge should not be hot removable 
under any
conditions. Hence, this patch tries to address this. After the change, as the 
demo video
shows, Windows no longer shows the bridge device as hot removable:  
https://youtu.be/kbgej5B9Hgs
under the same test settings.

Requesting comments for this fix.

--Ani