platforms/ibm-fsp: Reuse PCI slot mechanism for fixup
platforms/ibm-fsp: Reuse PCI slot mechanism for fixup

Currently, we have separately I2C stubs used for PCI slot power
management and fixup. It's reasonable to merge them to one so
that the code looks unified. Also, this introduces a table tracking
PCI slot fixup info which is very easy to be extended in future.

Signed-off-by: Gavin Shan <0398910e4f4970259b451f0f9d0686cc5e961b81@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

shenki/skiboot,legoater/skiboot,shenki/skiboot,shenki/skiboot,qemu/skiboot,shenki/skiboot,mikey/skiboot,open-power/skiboot,mikey/skiboot,legoater/skiboot,legoater/skiboot,stewart-ibm/skiboot,shenki/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,mikey/skiboot,qemu/skiboot,stewart-ibm/skiboot,qemu/skiboot,open-power/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,stewart-ibm/skiboot