hw/phb3: Override root slot's prepare_link_change() with PHB's
hw/phb3: Override root slot's prepare_link_change() with PHB's

For PCI slot behind root port, its prepare_link_change() should be
same to PHB's. Otherwise, the UTL events cannot be masked when the
slot is reseted, leading to EEH error because of UTL link-down
event.

Cc: stable # 5.3.0+
Signed-off-by: Gavin Shan <0398910e4f4970259b451f0f9d0686cc5e961b81@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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