PSI: Reorganize PSI link down handling code
PSI: Reorganize PSI link down handling code

Remove some code duplication and correct sequence handling.

Signed-off-by: Ananth N Mavinakayanahalli <7dc108d19a2513f6455353af182b9e4d3b794ec9@in.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>

legoater/skiboot,ddstreet/skiboot,mikey/skiboot,qemu/skiboot,csmart/skiboot,mikey/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,legoater/skiboot,neelegup/skiboot,open-power/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,jk-ozlabs/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,csmart/skiboot,shenki/skiboot,apopple/skiboot,stewart-ibm/skiboot,cyrilbur-ibm/skiboot,open-power/skiboot,ddstreet/skiboot,stewart-ibm/skiboot,apopple/skiboot,neelegup/skiboot,csmart/skiboot,apopple/skiboot,open-power/skiboot,qemu/skiboot,cyrilbur-ibm/skiboot,jk-ozlabs/skiboot,mikey/skiboot,qemu/skiboot,neelegup/skiboot,stewart-ibm/skiboot,cyrilbur-ibm/skiboot,legoater/skiboot,shenki/skiboot,jk-ozlabs/skiboot,ddstreet/skiboot