PSI: Drive link down on HIR

After sending the FSP reset sequence via PSIHBCR, drive the PSI link down
without actually waiting for the PSI interrupt indicating the
'Link Inactive Transition'.

There have been cases where this interrupt doesn't arrive and we are left
high and dry waiting for it, while the FSP comes back up and thinks Sapphire
is not initializing the new link (bz 117526 for instance).

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>